diff --git a/.gitignore b/.gitignore
index b8bd026..06e7ff6 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,52 @@
+# -*- mode: gitignore; -*-
+*~
+\#*\#
+/.emacs.desktop
+/.emacs.desktop.lock
+*.elc
+auto-save-list
+tramp
+.\#*
+
+# Org-mode
+.org-id-locations
+*_archive
+
+# flymake-mode
+*_flymake.*
+
+# eshell files
+/eshell/history
+/eshell/lastdir
+
+# elpa packages
+/elpa/
+
+# reftex files
+*.rel
+
+# AUCTeX auto folder
+/auto/
+
+# cask packages
+.cask/
+dist/
+
+# Flycheck
+flycheck_*.el
+
+# server auth directory
+/server/
+
+# projectiles files
+.projectile
+
+# directory configuration
+.dir-locals.el
+
+# Prerequisites
+*.d
+
 # Compiled Object files
 *.slo
 *.lo
@@ -15,6 +64,7 @@
 
 # Fortran module files
 *.mod
+*.smod
 
 # Compiled Static libraries
 *.lai
@@ -25,4 +75,4 @@
 # Executables
 *.exe
 *.out
-*.app
+*.app
\ No newline at end of file
diff --git a/Ch 1.Arrays And Strings/1.Is Unique/1. Is_unique.cpp b/Ch 1.Arrays And Strings/1.Is Unique/1. Is_unique.cpp
deleted file mode 100644
index 6118cc1..0000000
--- a/Ch 1.Arrays And Strings/1.Is Unique/1. Is_unique.cpp	
+++ /dev/null
@@ -1,70 +0,0 @@
-#include <string>
-#include <vector>
-#include <iostream>
-#include <bitset>
-#include <algorithm> // for sort() 
-
-using namespace std;
-
-bool isUniqueChars(const string &str){
-		if (str.length() > 128){
-			return false;
-		}
-		vector<bool> char_set(128);
-		for (int i = 0; i < str.length(); i++){
-			int val = str[i];
-			if (char_set[val]){
-				return false;
-			}
-			char_set[val] = true;
-		}
-		return true;
-}
-
-bool isUniqueChars_bitvector(const string &str) {
-	//Reduce space usage by a factor of 8 using bitvector. 
-	//Each boolean otherwise occupies a size of 8 bits.
-	bitset<256> bits(0);
-	for(int i = 0; i < str.length(); i++) {
-		int val = str[i];
-		if(bits.test(val) > 0) {
-			return false;
-		}
-		bits.set(val);
-	}
-	return true;
-}
-bool isUniqueChars_noDS( string str) {
-	
-	sort(str.begin(), str.end()); // O(nlogn) sort from <algorithm>
-
-	bool noRepeat = true;
-	for ( int i = 0 ; i < str.size() - 1; i++){
-		if ( str[i] == str[i+1] ){
-			noRepeat = false;
-			break;
-		}
-	}
-
-	return noRepeat;	
-}
-
-int main(){
-		vector<string> words = {"abcde", "hello", "apple", "kite", "padle"};
-		for (auto word : words)
-		{
-			cout << word << string(": ") << boolalpha << isUniqueChars(word) <<endl;
-		}
-		cout <<endl << "Using bit vector" <<endl;
-		for (auto word : words)
-		{
-			cout << word << string(": ") << boolalpha << isUniqueChars_bitvector(word) <<endl;
-		}
-		cout <<endl << "Using no Data Structures" <<endl;
-		for (auto word : words)
-		{
-			cout << word << string(": ") << boolalpha << isUniqueChars_noDS(word) <<endl;
-		}
-		return 0;
-}
-
diff --git a/Ch 1.Arrays And Strings/2.Check Permutation/1.Check_Permutation.cpp b/Ch 1.Arrays And Strings/2.Check Permutation/1.Check_Permutation.cpp
deleted file mode 100644
index 014899d..0000000
--- a/Ch 1.Arrays And Strings/2.Check Permutation/1.Check_Permutation.cpp	
+++ /dev/null
@@ -1,75 +0,0 @@
-#include <stdio.h>
-#include <string.h>
-#include <algorithm>
-#include <iostream>
-using namespace std;
-bool arePermutation(string str1,string str2)
-{
-    // Get lengths of both strings
-    int n1 = str1.length();
-    int n2 = str2.length();
-
-    // If length of both strings is not same, then they
-    // cannot be anagram
-    if (n1 != n2)
-      return false;
-
-    // Sort both strings
-    sort(str1.begin(), str1.end());
-    sort(str2.begin(), str2.end());
-    // Compare sorted strings
-    for (int i = 0; i < n1;  i++)
-       if (str1[i] != str2[i])
-         return false;
-
-    return true;
-}
-
-bool arePermutation_2(const string &str1, const string &str2) {
-  if(str1.length() != str2.length()) 
-    return false;
-  int count[256]={0};
-  for(int i = 0; i < str1.length(); i++) {
-    int val = str1[i];
-    count[val]++;
-  }
-  for(int i = 0; i < str2.length(); i++) {
-    int val = str2[i];
-    count[val]--;
-    if(count[val]<0) 
-      return false;
-  }
-  return true;
-}
-int main() {
-// Test Method 1 - Using sort
-    cout << "Method 1 - Using sort" << endl;
-    string str1 = "testest";
-    string str2 = "estxest";
-    if(arePermutation(str1, str2))
-      cout << str1 <<" and " << str2 << " are permutation of each other" << endl;
-    else
-      cout << str1 <<" and " << str2 << " are not permutation of each other" << endl;
-    str1 = "hello";
-    str2 = "oellh";
-    if(arePermutation(str1, str2))
-      cout << str1 <<" and " << str2 << " are permutation of each other" << endl;
-    else
-      cout << str1 <<" and " << str2 << " are not permutation of each other" << endl;
-
-//Test Method 2 - Using character count
-    cout << "Method 2 - Using character count" << endl;
-    str1 = "testest";
-    str2 = "estxest";
-    if(arePermutation_2(str1, str2))
-      cout << str1 <<" and " << str2 << " are permutation of each other" << endl;
-    else
-      cout << str1 <<" and " << str2 << " are not permutation of each other" << endl;
-    str1 = "hello";
-    str2 = "oellh";
-     if(arePermutation_2(str1, str2))
-      cout << str1 <<" and " << str2 << " are permutation of each other" << endl;
-    else
-      cout << str1 <<" and " << str2 << " are not permutation of each other" << endl;
-    return 0;
-}
diff --git a/Ch 1.Arrays And Strings/3.Palindrome Permutation/Palindrome Permutation.cpp b/Ch 1.Arrays And Strings/3.Palindrome Permutation/Palindrome Permutation.cpp
deleted file mode 100644
index f9a5511..0000000
--- a/Ch 1.Arrays And Strings/3.Palindrome Permutation/Palindrome Permutation.cpp	
+++ /dev/null
@@ -1,64 +0,0 @@
-#include <string>
-#include <vector>
-#include <iostream>
-
-using namespace std;
-
-int getCharNumber(const char & c){
-    int a = (int) 'a';
-    int z = (int) 'z';
-    int A = (int) 'A';
-    int Z = (int) 'Z';
-    int val = (int) c;
-    if(a <= val && val <= z){
-        return val - 'a';
-    }
-    else if(A <= val && val <= Z){
-        return val - 'A';
-    }
-    return -1;
-}
-
-
-vector <int> buildCharFrequencyTable(string phrase){
-    vector <int> table(getCharNumber('z') - getCharNumber('a') + 1, 0);
-    for(char &c : phrase){
-        int x = getCharNumber(c);
-        if(x != -1){
-            table[x]++;
-        }
-    }
-    return table;
-}
-
-
-bool checkMaxOneOdd(vector<int> &table)
-{
-    bool foundOdd = false;
-    for (auto count : table)
-    {
-        if (count % 2 == 1)
-        {
-            if (foundOdd)
-            {
-                return false;
-            }
-            foundOdd = true;
-        }
-    }
-    return true;
-}
-
-bool isPermutationOfPalindrome(const string &phrase)
-{
-    vector<int> table = buildCharFrequencyTable(phrase);
-    return checkMaxOneOdd(table);
-}
-
-int main(int argc, const char *argv[])
-{
-    string pali = "Rats live on no evil star";
-    string isPermutation = isPermutationOfPalindrome(pali) ? "yes" : "no";
-    cout << isPermutation << endl;
-    return 0;
-}
diff --git a/Ch 1.Arrays And Strings/3.URLify/URLify.cpp b/Ch 1.Arrays And Strings/3.URLify/URLify.cpp
deleted file mode 100644
index 98f67b8..0000000
--- a/Ch 1.Arrays And Strings/3.URLify/URLify.cpp	
+++ /dev/null
@@ -1,47 +0,0 @@
-/*
- * Cracking the coding interview Edition 6
- * Problem 1.3 URLify --> Replace all the spaces in a string with '%20'. 
- * Assumption : We have enough space to accomodate addition chars
- * Preferebly in place
- */
-
-#include <iostream>
-#include <cstring>
-
-/*
- * Function : urlify
- * Args     : string long enough to accomodate extra chars + true len 
- * Return   : void (in place transformation of string)
- */
-
-void urlify(char *str, int len)
-{
-    int numOfSpaces = 0;
-    int i = 0, j = 0;
-    for ( i = 0; i < len; ++i ) {
-        if (str[i] == ' ') {
-            ++numOfSpaces;
-        }
-    }
-    
-    int extendedLen  = len + 2 * numOfSpaces;
-    i = extendedLen - 1;
-    for( j = len - 1; j >= 0; --j ) {
-        if ( str[j] != ' ' ) {
-           str[i--] = str[j];
-        } else {
-            str[i--] = '0';
-            str[i--] = '2';
-            str[i--] = '%';
-        }
-    }
-}
-
-int main()
-{
-    char str[] = "Mr John Smith    ";                       //String with extended length ( true length + 2* spaces)
-    std::cout << "Actual string   : " << str << std::endl;
-    urlify(str, 13);                                        //Length of "Mr John Smith" = 13
-    std::cout << "URLified string : " << str << std::endl;
-    return 0;
-}
diff --git a/Ch 1.Arrays And Strings/5. One Away/5.One Away.cpp b/Ch 1.Arrays And Strings/5. One Away/5.One Away.cpp
deleted file mode 100644
index 7ca6f1e..0000000
--- a/Ch 1.Arrays And Strings/5. One Away/5.One Away.cpp	
+++ /dev/null
@@ -1,41 +0,0 @@
-#include<string>
-#include<iostream>
-using namespace std;
-
-bool isOneAway(string s1, string s2){
-	string a,b;
-	a = s1.length() >= s2.length() ? s1 : s2;
-	b = s1.length() < s2.length() ? s1 : s2;
-	int len1, len2;
-	len1 = a.length();
-	len2 = b.length();
-	if(abs(len1-len2)>1)
-		return false;
-	
-	bool flag = false;
-	for(int i=0,j=0;i<len1 && j<len2;){
-		if(a[i]!=b[j]){
-			if(flag)
-				return false;
-			flag = true;
-			if(len1 == len2)
-				i++,j++;
-			else
-				i++;
-		}
-		else
-			i++,j++;
-	}
-	return true;
-}
-
-int main(void){
-	string s1,s2;
-	getline(cin,s1);
-	getline(cin,s2);
-	if(isOneAway(s1,s2))
-		cout<<"One edit away."<<endl;
-	else
-		cout<<"Not one edit away."<<endl;
-	return 0;
-}
diff --git a/Ch 1.Arrays And Strings/5.One_Away/5-one-edit-away.cpp b/Ch 1.Arrays And Strings/5.One_Away/5-one-edit-away.cpp
deleted file mode 100644
index 69a3d54..0000000
--- a/Ch 1.Arrays And Strings/5.One_Away/5-one-edit-away.cpp	
+++ /dev/null
@@ -1,82 +0,0 @@
-/* 
- * Problem: There are three possible edits that can be performed on a string.
- * 1. Insert a char.
- * 2. Delete a char.
- * 3. Replace a char.
- *
- * Given two strings, determine if they are one or 0 edit away.
- *
- * Approach :
- * 1. Case when strings are of some length --> possible edit is replace.
- *    If there are more than one mismatch, return false
- *
- * 2. Case when One string is bigger than another
- *    Smaller string ------------> Bigger String
- *                     insert
- *                     delete
- *    smaller string <-----------  Bigger String
- *
- *    Idea is check if there are more than one mismatch discounting the already
- *    difference in the string. Therefore for first mismatch we do not move the pointer
- *    pointing to smaller string, and then expect it to match from next char of bigger
- *    string.
- */
-
-
-
-#include <iostream>
-#include <string>
-#include <cmath>
-
-
-bool oneEditAway( const std::string & str1, const std::string & str2 )
-{
-    if ( std::abs( int(str1.length()) - int(str2.length()))  > 1 ) {
-        return false;
-    }
-
-    int len1 = str1.length();
-    int len2 = str2.length();
-    std::string smaller = len1 < len2 ? str1 : str2;
-    std::string bigger =  len1 < len2 ? str2 : str1;
-    
-    unsigned int i = 0, j = 0; 
-    bool mismatchDone = false;
-    while ( i < smaller.length() && j < bigger.length() )
-    {
-        if ( smaller[i] != bigger[j] ) {
-            if (mismatchDone) {
-                return false;
-            }
-            mismatchDone = true;
-            if ( len1 == len2 ) {
-                ++i;   //case of replace
-            }
-        } else {
-                ++i;   //move short pointer if its a match, dont move it in case of first mismatch
-        }
-        ++j;           //always move long string pointer.
-    }
-    return true;
-}
-
-
-void translate( bool result, const std::string str1, const std::string str2 )
-{
-    if (result == true ) {
-        std::cout << str1 << " and " << str2 << " are one edit away\n";
-    } else {
-        std::cout << str1 << " and " << str2 << " are not one edit away\n";
-    }
-}
-
-int main()
-{
-    translate ( oneEditAway("pale", "ple"), "pale", "ple" );
-    translate ( oneEditAway("pales", "pale"), "pales", "pale" );
-    translate ( oneEditAway("pale", "pales"), "pale", "pales" );
-    translate ( oneEditAway("pale", "bale"), "pale", "bale" );
-    translate ( oneEditAway("pale", "bake"), "pale", "bake" );
-    return 0;
-
-}
diff --git a/Ch 1.Arrays And Strings/6.String_Compression/6.string_compression.cpp b/Ch 1.Arrays And Strings/6.String_Compression/6.string_compression.cpp
deleted file mode 100644
index b9d70e6..0000000
--- a/Ch 1.Arrays And Strings/6.String_Compression/6.string_compression.cpp	
+++ /dev/null
@@ -1,52 +0,0 @@
-/*
- * Cracking the coding interview edition 6
- * Problem 1-6 Implement a method to perform basic string compression.
- * Example string aabcccccaaa should be compressed to a2b1c5a3,
- * however if compressed string is bigger than original string, return original string
- */
-
-#include <iostream>
-#include <string>
-
-
-std::string compress(std::string str)
-{
-	size_t original_length = str.length();
-	if (original_length < 2) {
-		return str;
-	}
-	std::string out{""};
-	int count = 1;
-	for( size_t i = 1; i < original_length; ++i ) {
-		if (str[i-1] == str[i]) {
-			++count;
-		} else {
-			out += str[i-1];
-			out += std::to_string(count);
-			count = 1;
-		}
-		if (out.length() >= original_length) {
-			return str;
-		}
-	}
-	out += str[original_length-1];
-	out += std::to_string(count);
-	if (out.length() >= original_length) {
-		return str;
-	}
-	return out;
-}
-
-int main()
-{
-	std::string str, out;
-	std::cout << "Enter a string:\n";
-	std::cin >> str;
-	out = compress(str);
-	if (str.compare(out)) {
-		std::cout << str << " can be compressed to " << out << std::endl;
-	} else {
-		std::cout << str << " can not be compressed\n";
-	}
-	return 0;
-}
diff --git a/Ch 1.Arrays And Strings/Q1_01_Is_Unique/isUnique.cpp b/Ch 1.Arrays And Strings/Q1_01_Is_Unique/isUnique.cpp
new file mode 100644
index 0000000..9814b97
--- /dev/null
+++ b/Ch 1.Arrays And Strings/Q1_01_Is_Unique/isUnique.cpp	
@@ -0,0 +1,69 @@
+#include <string>
+#include <vector>
+#include <iostream>
+#include <bitset>
+#include <algorithm> // for sort() 
+
+
+bool isUniqueChars(const std::string &str){
+  if (str.length() > 128){
+    return false;
+  }
+  std::vector<bool> charSet(128);
+  for (int i = 0; i < str.length(); i++){
+    int val = str[i];
+    if (charSet[val]){
+      return false;
+    }
+    charSet[val] = true;
+  }
+  return true;
+}
+
+bool isUniqueCharsBitVector(const std::string &str) {
+  //Reduce space usage by a factor of 8 using bitvector. 
+  //Each boolean otherwise occupies a size of 8 bits.
+  std::bitset<256> bits(0);
+  for(int i = 0; i < str.length(); i++) {
+    int val = str[i];
+    if(bits.test(val) > 0) {
+      return false;
+    }
+    bits.set(val);
+  }
+  return true;
+}
+bool isUniqueCharsNoDataStructure( std::string str) {
+  
+  std::sort(str.begin(), str.end()); // O(nlogn) sort from <algorithm>
+  
+  bool noRepeat = true;
+  for ( int i = 0 ; i < str.size() - 1; i++){
+    if ( str[i] == str[i+1] ){
+      noRepeat = false;
+      break;
+    }
+  }
+  
+  return noRepeat;	
+}
+
+int main(){
+  std::vector<std::string> words = {"abcde", "hello", "apple", "kite", "padle"};
+  for (auto word : words)
+    {
+      std::cout<<word<<": "<<isUniqueChars(word)<<std::endl;
+    }
+  std::cout<<std::endl<<"Using bit vector"<<std::endl;
+  for (auto word : words)
+    {
+      std::cout<<word<<": "<<isUniqueCharsBitVector(word)<<std::endl;
+    }
+  std::cout<<std::endl<<"Using no Data Structures"<<std::endl;
+  for (auto word : words)
+    {
+      std::cout<<word<<": "<<isUniqueCharsNoDataStructure(word)<<std::endl;
+    }
+  return 0;
+}
+
diff --git a/Ch 1.Arrays And Strings/Q1_02_Check_Permutation/checkPermutation.cpp b/Ch 1.Arrays And Strings/Q1_02_Check_Permutation/checkPermutation.cpp
new file mode 100644
index 0000000..6a2643c
--- /dev/null
+++ b/Ch 1.Arrays And Strings/Q1_02_Check_Permutation/checkPermutation.cpp	
@@ -0,0 +1,71 @@
+#include <stdio.h>
+#include <string.h>
+#include <algorithm>
+#include <iostream>
+
+bool arePermutation(std::string str1, std::string str2)
+{
+  // Get lengths of both strings
+  int n1 = str1.length();
+  int n2 = str2.length();
+  
+  // If length of both strings is not same, then they
+  // cannot be anagram
+  if (n1 != n2){
+    return false;
+  }
+  
+  // Sort both strings
+  sort(str1.begin(), str1.end());
+  sort(str2.begin(), str2.end());
+  // Compare sorted strings
+  for (int i = 0; i < n1;  i++){
+    if (str1[i] != str2[i]){
+      return false;
+    }
+  }
+  
+  return true;
+}
+
+bool arePermutation2(const std::string &str1, const std::string &str2) {
+  if(str1.length() != str2.length()){ 
+    return false;
+  }
+  int count[256]={0};
+  for(int i = 0; i < str1.length(); i++) {
+    int val = str1[i];
+    count[val]++;
+  }
+  for(int i = 0; i < str2.length(); i++) {
+    int val = str2[i];
+    count[val]--;
+    if(count[val]<0) 
+      return false;
+  }
+  return true;
+}
+int main() {
+  // Test Method 1 - Using sort
+  std::cout<<"Method 1 - Using sort"<< std::endl;
+  std::string str1 = "testest";
+  std::string str2 = "estxest";
+ 
+  std::cout<<str1<<", "<<str2<<": "<<arePermutation(str1, str2)<<std::endl;
+    
+  str1 = "hello";
+  str2 = "oellh";
+  std::cout<<str1<<", "<<str2<<": " <<arePermutation(str1, str2)<<std::endl;
+ 
+  //Test Method 2 - Using character count
+  std::cout << "Method 2 - Using character count" << std::endl;
+  str1 = "testest";
+  str2 = "estxest";
+ 
+  std::cout<<str1<<", "<<str2<<": "<<arePermutation2(str1, str2)<<std::endl;
+ 
+  str1 = "hello";
+  str2 = "oellh";
+  std::cout<<str1<<", "<<str2<<": "<<arePermutation2(str1, str2)<<std::endl;
+  return 0;
+}
diff --git a/Ch 1.Arrays And Strings/Q1_03_URLify/URLify.cpp b/Ch 1.Arrays And Strings/Q1_03_URLify/URLify.cpp
new file mode 100644
index 0000000..c44859f
--- /dev/null
+++ b/Ch 1.Arrays And Strings/Q1_03_URLify/URLify.cpp	
@@ -0,0 +1,47 @@
+/*
+ * Cracking the coding interview Edition 6
+ * Problem 1.3 URLify --> Replace all the spaces in a string with '%20'. 
+ * Assumption : We have enough space to accomodate addition chars
+ * Preferebly in place
+ */
+
+#include <iostream>
+#include <string>
+
+/*
+ * Function : urlify
+ * Args     : string long enough to accomodate extra chars + true len 
+ * Return   : void (in place transformation of string)
+ */
+
+void urlify(std::string &str, const int &len)
+{
+  int numOfSpaces = 0;
+  int i = 0, j = 0;
+  for ( i = 0; i < len; i++ ) {
+    if (str[i] == ' ') {
+      numOfSpaces++;
+    }
+  }
+  
+  int extendedLen  = len + 2 * numOfSpaces;
+  i = extendedLen - 1;
+  for( j = len - 1; j >= 0; j-- ) {
+    if ( str[j] != ' '  ) {
+      str[i--] = str[j];
+    } else {
+      str[i--] = '0';
+      str[i--] = '2';
+      str[i--] = '%';
+    }
+  }
+}
+
+int main()
+{
+  std::string str = "Mr John Smith    ";                       //String with extended length ( true length + 2* spaces)
+  std::cout<<"Actual string   : "<<str<<std::endl;
+  urlify(str, 13);                                        //Length of "Mr John Smith" = 13
+  std::cout<<"URLified string : "<<str<<std::endl;
+  return 0;
+}
diff --git a/Ch 1.Arrays And Strings/4.Palindrome_Permutation/4-pallindrome-permutations.cpp b/Ch 1.Arrays And Strings/Q1_04_Palindrome_Permutation/palindromePermutation.cpp
similarity index 75%
rename from Ch 1.Arrays And Strings/4.Palindrome_Permutation/4-pallindrome-permutations.cpp
rename to Ch 1.Arrays And Strings/Q1_04_Palindrome_Permutation/palindromePermutation.cpp
index b2084f1..795bfb7 100644
--- a/Ch 1.Arrays And Strings/4.Palindrome_Permutation/4-pallindrome-permutations.cpp	
+++ b/Ch 1.Arrays And Strings/Q1_04_Palindrome_Permutation/palindromePermutation.cpp	
@@ -12,7 +12,7 @@
  */
 
 #include <iostream>
-
+#include <vector>
 
 /*
  * Helper routine to return an frequency Table index
@@ -21,35 +21,37 @@
 
 int getCharIndex( char c )
 {
-    int idx = -1;
-    if ( c >= 'a' && c <= 'z' )
+  int idx = -1;
+  if ( c >= 'a' && c <= 'z' )
     {
-        idx = c - 'a';
+      idx = c - 'a';
     }
-    else if ( c >= 'A' && c <= 'Z' )
+  else if ( c >= 'A' && c <= 'Z' )
     {
-        idx = c - 'A';
+      idx = c - 'A';
     }
-    return idx;
+  return idx;
 }
 
 /*
  * Function : countFrequency
  * Args     : input string, an array of int 
- * Return   : Void, array of int will populate each letter's frequency in string.
+ * Return   : vector of int will populate each letter's frequency in string.
  */
 
-void countFrequency( const std::string & str, int *frequency )
+std::vector<int> countFrequency( const std::string & str)
 {
-    int idx;
-    for (const char & c : str)
+  std::vector<int> frequency(26,0);
+  int idx;
+  for (const char & c : str)
     {
-        idx = getCharIndex(c);
-        if ( idx != -1 )
+      idx = getCharIndex(c);
+      if ( idx != -1 )
         {
-            ++frequency[idx];
+	  frequency[idx]++;
         }
     }
+  return frequency;
 }
 
 
@@ -62,22 +64,21 @@ void countFrequency( const std::string & str, int *frequency )
 
 bool isPermutationOfPallindrome1( const std::string & str )
 {
-    int frequency[ 26 ] = { 0 };
-    countFrequency( str, frequency );
+  std::vector<int> frequency = countFrequency(str);
 
     /*
      * We will check here that letter frequencies are all even or all even except one odd.
      */
-    bool oddAppeared = false;
-    std::cout << std::endl;
-    for ( int i = 0 ; i < 26; ++i ) {
-        if ( frequency[i] % 2  && oddAppeared ) {
-            return false;
-        } else if ( frequency[i] % 2 && !oddAppeared ) {
-            oddAppeared = true;
-        }
+  bool oddAppeared = false;
+  std::cout << std::endl;
+  for ( int i = 0 ; i < 26; ++i ) {
+    if ( frequency[i] % 2  && oddAppeared ) {
+      return false;
+    } else if ( frequency[i] % 2 && !oddAppeared ) {
+      oddAppeared = true;
     }
-    return true;
+  }
+  return true;
 }
 
 
@@ -90,24 +91,24 @@ bool isPermutationOfPallindrome1( const std::string & str )
 
 bool isPermutationOfPallindrome2( const std::string & str )
 {
-    int oddCount = 0;
-    int frequency[26] = { 0 };
-    int idx = 0;
-    for ( const char & c : str )
+  int oddCount = 0;
+  int frequency[26] = { 0 };
+  int idx = 0;
+  for ( const char & c : str )
     {
-        idx = getCharIndex(c);
-        if ( idx != -1 )
+      idx = getCharIndex(c);
+      if ( idx != -1 )
         {
-            ++frequency[idx];
-            if ( frequency[idx] % 2 ) 
+	  frequency[idx]++;
+	  if ( frequency[idx] % 2 ) 
             {   
-                ++oddCount;
+	      ++oddCount;
             } else {
-                --oddCount;
-            }
+	    oddCount--;
+	  }
         }
     }
-    return (oddCount <= 1);
+  return (oddCount <= 1);
 }
 
 /*
@@ -126,18 +127,18 @@ bool isPermutationOfPallindrome2( const std::string & str )
 
 int toggle( int bitVector, int index )
 {
-    if ( index < 0 )
-        return bitVector;
-
-    int mask = 1 << index;
-    //if bit is not set
-    if ( (bitVector & mask ) == 0 )
+  if ( index < 0 ){
+    return bitVector;
+  }
+  int mask = 1 << index;
+  //if bit is not set
+  if ( (bitVector & mask ) == 0 )
     {
-        bitVector |= mask;
+      bitVector |= mask;
     } else {    //if bit is set
-        bitVector &= ~mask;
-    }
-    return bitVector;
+    bitVector &= ~mask;
+  }
+  return bitVector;
 }
 
 /*
diff --git a/Ch 1.Arrays And Strings/Q1_05_One_Away/oneAway.cpp b/Ch 1.Arrays And Strings/Q1_05_One_Away/oneAway.cpp
new file mode 100644
index 0000000..5bc5aba
--- /dev/null
+++ b/Ch 1.Arrays And Strings/Q1_05_One_Away/oneAway.cpp	
@@ -0,0 +1,82 @@
+/* 
+ * Problem: There are three possible edits that can be performed on a string.
+ * 1. Insert a char.
+ * 2. Delete a char.
+ * 3. Replace a char.
+ *
+ * Given two strings, determine if they are one or 0 edit away.
+ *
+ * Approach :
+ * 1. Case when strings are of some length --> possible edit is replace.
+ *    If there are more than one mismatch, return false
+ *
+ * 2. Case when One string is bigger than another
+ *    Smaller string ------------> Bigger String
+ *                     insert
+ *                     delete
+ *    smaller string <-----------  Bigger String
+ *
+ *    Idea is check if there are more than one mismatch discounting the already
+ *    difference in the string. Therefore for first mismatch we do not move the pointer
+ *    pointing to smaller string, and then expect it to match from next char of bigger
+ *    string.
+ */
+
+
+
+#include <iostream>
+#include <string>
+#include <cmath>
+
+
+bool oneEditAway( const std::string & str1, const std::string & str2 )
+{
+  if ( std::abs( int(str1.length()) - int(str2.length()))  > 1 ) {
+    return false;
+  }
+  
+  int len1 = str1.length();
+  int len2 = str2.length();
+  std::string smaller = len1 < len2 ? str1 : str2;
+  std::string bigger =  len1 < len2 ? str2 : str1;
+  
+  unsigned int i = 0, j = 0; 
+  bool mismatchDone = false;
+  while ( i < smaller.length() && j < bigger.length() )
+    {
+      if ( smaller[i] != bigger[j] ) {
+	if (mismatchDone) {
+	  return false;
+	}
+	mismatchDone = true;
+	if ( len1 == len2 ) {
+	  ++i;   //case of replace
+	}
+      } else {
+	++i;   //move short pointer if its a match, dont move it in case of first mismatch
+      }
+      ++j;           //always move long string pointer.
+    }
+  return true;
+}
+
+
+void translate( bool result, const std::string str1, const std::string str2 )
+{
+    if (result == true ) {
+      std::cout << str1 << " and " << str2 << " are one edit away\n";
+    } else {
+      std::cout << str1 << " and " << str2 << " are not one edit away\n";
+    }
+}
+
+int main()
+{
+  translate ( oneEditAway("pale", "ple"), "pale", "ple" );
+  translate ( oneEditAway("pales", "pale"), "pales", "pale" );
+  translate ( oneEditAway("pale", "pales"), "pale", "pales" );
+  translate ( oneEditAway("pale", "bale"), "pale", "bale" );
+  translate ( oneEditAway("pale", "bake"), "pale", "bake" );
+  return 0;
+  
+}
diff --git a/Ch 1.Arrays And Strings/Q1_06_String_Compression/stringCompression.cpp b/Ch 1.Arrays And Strings/Q1_06_String_Compression/stringCompression.cpp
new file mode 100644
index 0000000..daf2f35
--- /dev/null
+++ b/Ch 1.Arrays And Strings/Q1_06_String_Compression/stringCompression.cpp	
@@ -0,0 +1,53 @@
+/*
+ * Cracking the coding interview edition 6
+ * Problem 1-6 Implement a method to perform basic string compression.
+ * Example string aabcccccaaa should be compressed to a2b1c5a3,
+ * however if compressed string is bigger than original string, return original string
+ */
+
+#include <iostream>
+#include <string>
+
+
+std::string compress(std::string str)
+{
+  size_t original_length = str.length();
+  if (original_length < 2) {
+    return str;
+  }
+  std::string out{""};
+  int count = 1;
+  for( size_t i = 1; i < original_length; ++i ) {
+    if (str[i-1] == str[i]) {
+      ++count;
+    } else {
+      out += str[i-1];
+      out += std::to_string(count);
+      count = 1;
+    }
+    
+    if (out.length() >= original_length) {
+      return str;
+    }
+  }
+  out += str[original_length-1];
+  out += std::to_string(count);
+  if (out.length() >= original_length) {
+    return str;
+  }
+  return out;
+}
+
+int main()
+{
+  std::string str, out;
+  std::cout << "Enter a string:\n";
+  std::cin >> str;
+  out = compress(str);
+  if (str.compare(out)) {
+    std::cout << str << " can be compressed to " << out << std::endl;
+  } else {
+    std::cout << str << " can not be compressed\n";
+  }
+  return 0;
+}
diff --git a/Ch 1.Arrays And Strings/7.Rotate_matrix/7.rotate_matrix.cpp b/Ch 1.Arrays And Strings/Q1_07_Rotate_Matrix/7.rotate_matrix.cpp
similarity index 100%
rename from Ch 1.Arrays And Strings/7.Rotate_matrix/7.rotate_matrix.cpp
rename to Ch 1.Arrays And Strings/Q1_07_Rotate_Matrix/7.rotate_matrix.cpp
diff --git a/Ch 1.Arrays And Strings/8.Zero_matrix/8.zero_matrix.cpp b/Ch 1.Arrays And Strings/Q1_08_Zero_Matrix/8.zero_matrix.cpp
similarity index 100%
rename from Ch 1.Arrays And Strings/8.Zero_matrix/8.zero_matrix.cpp
rename to Ch 1.Arrays And Strings/Q1_08_Zero_Matrix/8.zero_matrix.cpp
diff --git a/Ch 1.Arrays And Strings/9.String_rotation/9.string_rotation.cpp b/Ch 1.Arrays And Strings/Q1_09_String_Rotation/9.string_rotation.cpp
similarity index 100%
rename from Ch 1.Arrays And Strings/9.String_rotation/9.string_rotation.cpp
rename to Ch 1.Arrays And Strings/Q1_09_String_Rotation/9.string_rotation.cpp