diff --git a/Array/CheckArrayFormationThroughConcatenation.swift b/Array/CheckArrayFormationThroughConcatenation.swift
new file mode 100644
index 00000000..9827dccc
--- /dev/null
+++ b/Array/CheckArrayFormationThroughConcatenation.swift
@@ -0,0 +1,8 @@
+class Solution {
+    func canFormArray(_ arr: [Int], _ pieces: [[Int]]) -> Bool {
+        var map = pieces.reduce(into: [Int:[Int]]()) { $0[arr.firstIndex(of: $1[0]) ?? 0] = $1 }
+        var smap = Array(map.sorted { $0.0 < $1.0 }.flatMap{ $0.1 })
+        
+        return arr.hashValue == smap.hashValue
+    }
+}
\ No newline at end of file
diff --git a/Array/MaxNumberOfK-SumPairs.swift b/Array/MaxNumberOfK-SumPairs.swift
new file mode 100644
index 00000000..2bc399e0
--- /dev/null
+++ b/Array/MaxNumberOfK-SumPairs.swift
@@ -0,0 +1,16 @@
+class Solution {
+    func maxOperations(_ nums: [Int], _ k: Int) -> Int {
+        var rest = [Int: Int]()
+        var result = 0
+        for num in nums {
+            if let count = rest[k-num], count > 0 {
+                rest[k-num] = count-1
+                result += 1
+            } else {
+                rest[num, default: 0] += 1
+            }
+        }
+        
+        return result
+    }
+}
\ No newline at end of file
diff --git a/BFS/JumpGameIV.swift b/BFS/JumpGameIV.swift
new file mode 100644
index 00000000..c36540ce
--- /dev/null
+++ b/BFS/JumpGameIV.swift
@@ -0,0 +1,49 @@
+class Solution {
+    func minJumps(_ arr: [Int]) -> Int {
+        var map = [Int: [Int]]()
+        for i in 0..<arr.count {
+            map[arr[i], default: [Int]()].append(i)
+        }
+        
+        var visited = Array(repeating: false, count: arr.count)
+        visited[0] = true
+        var steps = [0]
+        
+        func appendQueue(_ index: Int) {
+            if !visited[index] {
+                steps.append(index)
+                visited[index] = true
+            }
+        }
+        
+        for currentStep in 1...arr.count {
+            let doSteps = steps
+            steps = []
+            for num in doSteps {
+                // Reach
+                if num == (arr.count-1) { 
+                    return currentStep-1 
+                }
+                
+                // Right 
+                if num < (arr.count-1) {
+                    appendQueue(num+1)
+                }
+                
+                // Left
+                if num > 0 {
+                    appendQueue(num-1)
+                }
+                
+                // Tail
+                let datas = map[arr[num]]!
+                for data in datas {
+                    appendQueue(data)
+                }
+                map[arr[num]] = []
+            }
+        }
+        
+        return 0
+    }
+}
\ No newline at end of file
diff --git a/DFS/BeautifulArrangement.swift b/DFS/BeautifulArrangement.swift
new file mode 100644
index 00000000..b6ee9f11
--- /dev/null
+++ b/DFS/BeautifulArrangement.swift
@@ -0,0 +1,21 @@
+class Solution {
+    func countArrangement(_ n: Int) -> Int {
+        var arr = Array(repeating: false, count: n)
+        return countArr(1, &arr)
+    }
+    
+    func countArr(_ c: Int, _ arr: inout [Bool]) -> Int {
+        if c > arr.count { return 1 }
+        
+        var count = 0
+        for x in 0..<arr.count {
+            if !arr[x] && ((x+1) % c == 0 || c % (x+1) == 0) {
+                arr[x] = true
+                count += countArr(c+1, &arr)
+                arr[x] = false
+            }
+        }
+        
+        return count
+    }
+}
\ No newline at end of file
diff --git a/DP/BoatsToSavePeople.swift b/DP/BoatsToSavePeople.swift
new file mode 100644
index 00000000..edb8b9bc
--- /dev/null
+++ b/DP/BoatsToSavePeople.swift
@@ -0,0 +1,17 @@
+class Solution {
+    func numRescueBoats(_ people: [Int], _ limit: Int) -> Int {
+        var people = people.sorted()
+        var result = people.count
+        var l = 0, r = result-1
+        
+        while l < r {
+            if people[l] + people[r] <= limit {
+                l += 1
+                result -= 1
+            }
+            r -= 1
+        }
+        
+        return result
+    }
+}
diff --git a/DP/CountSortedVowelStrings.swift b/DP/CountSortedVowelStrings.swift
new file mode 100644
index 00000000..aa921901
--- /dev/null
+++ b/DP/CountSortedVowelStrings.swift
@@ -0,0 +1,21 @@
+class Solution {
+    func countVowelStrings(_ n: Int) -> Int {
+        var curr = [0, 0, 0, 0, 1]
+        
+        for _ in 1..<n {
+            var next = [Int]()
+            var sum = 0
+            for x in (0..<curr.count).reversed() {
+                sum += curr[x]
+                next.insert(sum, at:0)
+            }
+            curr = next
+        }
+        
+        var result = 0
+        for x in 0..<curr.count {
+            result += curr[x] * (x+1)
+        }
+        return result
+    }
+}
\ No newline at end of file
diff --git a/DP/MinimumOperationsToReduceXToZero.swift b/DP/MinimumOperationsToReduceXToZero.swift
new file mode 100644
index 00000000..ebb1f7df
--- /dev/null
+++ b/DP/MinimumOperationsToReduceXToZero.swift
@@ -0,0 +1,25 @@
+class Solution {
+    func minOperations(_ nums: [Int], _ x: Int) -> Int {
+        var leftSums = [0: 0]
+        
+        var leftSum = 0
+        for l in 0..<nums.count {
+            leftSum += nums[l]
+            if leftSums[leftSum] == nil {
+                leftSums[leftSum] = l + 1
+            }
+        }
+        
+        var result = leftSums[x, default: Int.max]
+        
+        var rightSum = 0
+        for r in (0..<nums.count).reversed() {
+            rightSum += nums[r]
+            if let l = leftSums[x-rightSum], r > l {
+               result = min(result, l + nums.count - r)
+            }
+        }
+        
+        return result < Int.max ? result : -1
+    }
+}
\ No newline at end of file
diff --git a/LinkedList/PseudoPalindromicPathsInABinaryTree.swift b/LinkedList/PseudoPalindromicPathsInABinaryTree.swift
new file mode 100644
index 00000000..d8beeff5
--- /dev/null
+++ b/LinkedList/PseudoPalindromicPathsInABinaryTree.swift
@@ -0,0 +1,58 @@
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public var val: Int
+ *     public var left: TreeNode?
+ *     public var right: TreeNode?
+ *     public init() { self.val = 0; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
+ *     public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
+ *         self.val = val
+ *         self.left = left
+ *         self.right = right
+ *     }
+ * }
+ */
+class Solution {
+    func pseudoPalindromicPaths (_ root: TreeNode?) -> Int {
+        var count = 0
+        goPath(Box(node: root!, path: [root!.val]), &count)
+        return count
+    }
+    
+    func goPath(_ box: Box, _ count: inout Int) {
+        if box.node.left == nil && box.node.right == nil {
+            if box.path.count < 2 { count += 1 }
+            return
+        }
+        
+        if box.node.left != nil {
+            var lBox = box
+            let lVal = lBox.node.left!.val
+            if lBox.path.contains(lVal) {
+                lBox.path.remove(lVal)
+            } else {
+                lBox.path.insert(lVal)
+            }
+            lBox.node = lBox.node.left!
+            goPath(lBox, &count)
+        }
+        
+        if box.node.right != nil {
+            var rBox = box
+            let rVal = rBox.node.right!.val
+            if rBox.path.contains(rVal) {
+                rBox.path.remove(rVal)
+            } else {
+                rBox.path.insert(rVal)
+            }
+            rBox.node = rBox.node.right!
+            goPath(rBox, &count)
+        }
+    }
+    
+    struct Box {
+        var node: TreeNode
+        var path: Set<Int>
+    }
+}
\ No newline at end of file
diff --git a/Math/ReachANumber.swift b/Math/ReachANumber.swift
new file mode 100644
index 00000000..6b419480
--- /dev/null
+++ b/Math/ReachANumber.swift
@@ -0,0 +1,26 @@
+class Solution {
+    func reachNumber(_ target: Int) -> Int {
+        var target = abs(target)
+        
+        var step = 0
+        while target > 0 {
+            step += 1
+            target -= step
+        }
+        target = -target
+        
+        return (target.isMultiple(of: 2) ? step : (step + 1 + step%2))
+    }
+}
+
+/*
+0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21
+    1       2           3               4                   5                       6
+    2           3               4                   5                       6
+        3               4                   5                       6
+3               4                   5                       6
+        4                   5                       6
+4                   5                       6
+*/
+
+
diff --git a/README.md b/README.md
index 97a0cc4c..970ed554 100644
--- a/README.md
+++ b/README.md
@@ -42,8 +42,10 @@
 ## Array
 | Title | Solution | Difficulty | Time | Space |
 | ----- | -------- | ---------- | ---- | ----- |
+[Max Number of K-Sum Pairs](https://leetcode.com/problems/max-number-of-k-sum-pairs/)|[Swift](./Array/MaxNumberOfK-SumPairs.swift)| Medium| O(n)| O(n)|
+[Check Array Formation Through Concatenation](https://leetcode.com/problems/check-array-formation-through-concatenation/)|[Swift](./Array/CheckArrayFormationThroughConcatenation.swift)| Easy| O(nlogn)| O(n)|
 [Verify an Alien Dictionary](https://leetcode.com/problems/verifying-an-alien-dictionary/)|[Swift](Array/VerifyingAlienDictionary.swift)| Easy| O(n)| O(n)|
-[Sort Array By Parity](https://leetcode.com/problems/sort-array-by-parity/)|[Swift](Array/SortArrayByParity.swift)| Easy| O(n)| O(n)|
+[Sort Array By Parity](https://leetcode.com/problems/sort-array-by-parity/)|[Swift](./Array/SortArrayByParity.swift)| Easy| O(n)| O(n)|
 [Max Consecutive Ones](https://leetcode.com/problems/max-consecutive-ones/)| [Swift](./Array/MaxConsecutiveOnes.swift)| Easy| O(n)| O(1)|
 [Heaters](https://leetcode.com/problems/heaters/)| [Swift](./Array/Heaters.swift)| Easy| O(nlogn)| O(1)|
 [Number of Boomerangs](https://leetcode.com/problems/number-of-boomerangs/)| [Swift](./Array/NumberBoomerangs.swift)| Easy| O(n ^ 2)| O(n)|
@@ -102,6 +104,7 @@
 ## String
 | Title | Solution | Difficulty | Time | Space |
 | ----- | -------- | ---------- | ---- | ----- |
+[Determine if Two Strings Are Close](https://leetcode.com/problems/determine-if-two-strings-are-close/)| [Swift](./String/DetermineIfTwoStringsAreClose.swift)| Medium| O(n^2)| O(n)|
 [Fizz Buzz](https://leetcode.com/problems/fizz-buzz/)| [Swift](./String/FizzBuzz.swift)| Easy| O(n)| O(1)|
 [First Unique Character in a String](https://leetcode.com/problems/first-unique-character-in-a-string/)| [Swift](./String/FirstUniqueCharacterInString.swift)| Easy| O(n)| O(1)|
 [Keyboard Row](https://leetcode.com/problems/keyboard-row/)| [Swift](./String/KeyboardRow.swift)| Easy| O(nm)| O(n)|
@@ -159,10 +162,12 @@
 [Partition List](https://leetcode.com/problems/partition-list/)| [Swift](./LinkedList/PartitionList.swift)| Medium| O(n)| O(1)|
 [LRU Cache](https://leetcode.com/problems/lru-cache/) | [Swift](./LinkedList/LRUCache.swift) | Hard| O(1)| O(1)|
 [LFU Cache](https://leetcode.com/problems/lfu-cache/) | [Swift](./LinkedList/LFUCache.swift) | Hard| O(1)| O(1)|
+[Pseudo-Palindromic Paths in a Binary Tree](https://leetcode.com/problems/pseudo-palindromic-paths-in-a-binary-tree/) | [Swift](./LinkedList/PseudoPalindromicPathsInABinaryTree.swift) | Medium| O(n)| O(n)|
 
 ## Stack
 | Title | Solution | Difficulty | Time | Space |
 | ----- | -------- | ---------- | ---- | ----- |
+[Largest Rectangle in Histogram](https://leetcode.com/problems/largest-rectangle-in-histogram/)| [Swift](./Stack/LargestRectangleInHistogram.swift)| Hard| O(n)| O(n)|
 [Min Stack](https://leetcode.com/problems/min-stack/)| [Swift](./Stack/MinStack.swift)| Easy| O(1)| O(n)|
 [Max Stack](https://leetcode.com/problems/max-stack/)| [Swift](./Stack/MaxStack.swift)| Easy| O(n)| O(n)|
 [Valid Parentheses](https://leetcode.com/problems/valid-parentheses/)| [Swift](./Stack/ValidParentheses.swift)| Easy| O(n)| O(n)|
@@ -222,6 +227,9 @@
 ## Dynamic programming
 | Title | Solution | Difficulty | Time | Space |
 | ----- | -------- | ---------- | ---- | ----- |
+[Count Sorted Vowel Strings](https://leetcode.com/problems/count-sorted-vowel-strings/) | [Swift](./DP/CountSortedVowelStrings.swift)	| Medium| O(n)| O(n)|
+[Minimum Operations to Reduce X to Zero](https://leetcode.com/problems/minimum-operations-to-reduce-x-to-zero/) | [Swift](./DP/MinimumOperationsToReduceXToZero.swift)	| Medium| O(n)| O(n)|
+[Boats to Save People](https://leetcode.com/problems/boats-to-save-people/) | [Swift](./DP/BoatsToSavePeople.swift)	| Medium| O(nlogn)| O(n)|
 [Nested List Weight Sum](https://leetcode.com/problems/nested-list-weight-sum/)| [Swift](./DP/NestedListWeightSum.swift)| Easy| O(n)| O(1)|
 [Climbing Stairs](https://leetcode.com/problems/climbing-stairs/)| [Swift](./DP/ClimbingStairs.swift)| Easy| O(n)| O(1)|
 [Min Cost Climbing Stairs](https://leetcode.com/problems/min-cost-climbing-stairs/)| [Swift](./DP/MinCostClimbingStairs.swift)| Easy| O(n)| O(n)|
@@ -271,6 +279,7 @@
 ## Depth-first search
 | Title | Solution | Difficulty | Time | Space |
 | ----- | -------- | ---------- | ---- | ----- |
+[Beautiful Arrangement](https://leetcode.com/problems/beautiful-arrangement/)| [Swift](./DFS/BeautifulArrangement.swift)| Medium| O(n)| O(n)|
 [Permutations](https://leetcode.com/problems/permutations/)| [Swift](./DFS/Permutations.swift)| Medium| O(n^n)| O(n)|
 [Permutations II](https://leetcode.com/problems/permutations-ii/)| [Swift](./DFS/PermutationsII.swift)| Medium| O(n^n)| O(n)|
 [Subsets](https://leetcode.com/problems/subsets/)| [Swift](./DFS/Subsets.swift)| Medium| O(n^n)| O(n)|
@@ -305,6 +314,7 @@
 [Word Ladder](https://leetcode.com/problems/word-ladder/)| [Swift](./BFS/WordLadder.swift)| Medium| O(nm)| O(nm)|
 [Evaluate Division](https://leetcode.com/problems/evaluate-division/)| [Swift](./BFS/EvaluateDivision.swift)| Medium| O(n^2)| O(n)|
 [Shortest Distance from All Buildings](https://leetcode.com/problems/shortest-distance-from-all-buildings/)| [Swift](./BFS/ShortestDistanceAllBuildings.swift)| Hard| O((mn)^2)| O(mn)|
+[Jump Game IV](https://leetcode.com/problems/jump-game-iv/)| [Swift](./BFS/JumpGameIV.swift)| Hard| O(n)| O(n)|
 
 ## Math
 | Title | Solution | Difficulty | Time | Space |
@@ -348,6 +358,7 @@
 [Permutation Sequence](https://leetcode.com/problems/permutation-sequence/)| [Swift](./Math/PermutationSequence.swift)| Medium| O(n^2)| O(1)|
 [Line Reflection](https://leetcode.com/problems/line-reflection/)| [Swift](./Math/LineReflection.swift)| Medium| O(n)| O(n)|
 [Valid Number](https://leetcode.com/problems/valid-number/)| [Swift](./Math/ValidNumber.swift)| Hard| O(n)| O(1)|
+[Reach a Number](https://leetcode.com/problems/reach-a-number/)| [Swift](./Math/ReachANumber.swift)| Medium| O(logn)| O(1)|
 
 ## Search
 | Title | Solution | Difficulty | Time | Space |
@@ -540,8 +551,19 @@
 ## Problem Status
 | Solution | Number | Title | Difficulty |
 | -------- | ------ | ----- | ---------- |
+| [Swift](./Array/MaxNumberOfK-SumPairs.swift)	|	1679	|	[Max Number of K-Sum Pairs](https://leetcode.com/problems/max-number-of-k-sum-pairs/)	| Medium	|
+| [Swift](./DP/MinimumOperationsToReduceXToZero.swift)	|	1658	|	[Minimum Operations to Reduce X to Zero](https://leetcode.com/problems/minimum-operations-to-reduce-x-to-zero/)	| Medium	|
+| [Swift](./String/DetermineIfTwoStringsAreClose.swift)	|	1657	|	[Determine if Two Strings Are Close](https://leetcode.com/problems/determine-if-two-strings-are-close/)	| Medium	|
+| [Swift](./DP/CountSortedVowelStrings.swift)	|	1641	|	[Count Sorted Vowel Strings](https://leetcode.com/problems/count-sorted-vowel-strings/)	| Medium	|
+| [Swift](./Array/CheckArrayFormationThroughConcatenation.swift)	|	1640	|	[Check Array Formation Through Concatenation](https://leetcode.com/problems/check-array-formation-through-concatenation/)	| Easy	|
+| [Swift](./LinkedList/PseudoPalindromicPathsInABinaryTree.swift)	|	1457	|	[Pseudo-Palindromic Paths in a Binary Tree](https://leetcode.com/problems/pseudo-palindromic-paths-in-a-binary-tree/)	| Medium	|
+| [Swift](./BFS/JumpGameIV.swift)	|	1345	|	[Jump Game IV](https://leetcode.com/problems/jump-game-iv/)	| Hard	|
+| [Swift](./DP/BoatsToSavePeople.swift)	|	881	|	[Boats to Save People](https://leetcode.com/problems/boats-to-save-people/)	| Medium	|
+| [Swift](./Math/ReachANumber.swift)	|	754	|	[Reach a Number](https://leetcode.com/problems/reach-a-number/)	| Medium	|
+| [Swift](./DFS/BeautifulArrangement.swift)	|	526	|	[Beautiful Arrangement](https://leetcode.com/problems/beautiful-arrangement/)	| Medium	|
 | [Swift](./LinkedList/LFUCache.swift)	|	460	|	[LFU Cache](https://oj.leetcode.com/problems/lfu-cache/)	| Hard	|
 | [Swift](./Array/FindDisappearedNumbers.swift)| 448| [Find All Numbers Disappeared in an Array](https://leetcode.com/problems/find-all-numbers-disappeared-in-an-array/)| Easy|
+| [Swift](./String/FizzBuzz.swift)	|	412	|	[Fizz Buzz](https://leetcode.com/problems/fizz-buzz/)	|	Easy
 | [Swift](./DFS/CombinationSumIV.swift)	|	377	|	[Combination Sum IV](https://leetcode.com/problems/combination-sum-iv/)	|	Medium
 |		|	376	|	[Wiggle Subsequence](https://leetcode.com/problems/wiggle-subsequence/)	|	Medium
 |	[Swift](./DP/GuessNumberHigherOrLowerII.swift)	|	375	|	[Guess Number Higher or Lower II](https://leetcode.com/problems/guess-number-higher-or-lower-ii/)	|	Medium
@@ -818,7 +840,7 @@
 |		|	87	|	[Scramble String](https://oj.leetcode.com/problems/scramble-string/)	| Hard	|
 |	[Swift](./LinkedList/PartitionList.swift)	|	86	|	[Partition List](https://oj.leetcode.com/problems/partition-list/)	| Medium	|
 |		|	85	|	[Maximal Rectangle](https://oj.leetcode.com/problems/maximal-rectangle/)	| Hard	|
-|		|	84	|	[Largest Rectangle in Histogram](https://oj.leetcode.com/problems/largest-rectangle-in-histogram/)	| Hard	|
+|	[Swift](./Stack/LargestRectangleInHistogram.swift)	|	84	|	[Largest Rectangle in Histogram](https://leetcode.com/problems/largest-rectangle-in-histogram/)	| Hard	|
 |	[Swift](./LinkedList/RemoveDuplicatesFromSortedList.swift)	|	83	|	[Remove Duplicates from Sorted List](https://oj.leetcode.com/problems/remove-duplicates-from-sorted-list/)	| Easy	|
 |	[Swift](./LinkedList/RemoveDuplicatesFromSortedListII.swift)	|	82	|	[Remove Duplicates from Sorted List II](https://oj.leetcode.com/problems/remove-duplicates-from-sorted-list-ii/)	| Medium	|
 |	[Swift](./Search/SearchInRotatedSortedArrayII.swift)	|	81	|	[Search in Rotated Sorted Array II](https://oj.leetcode.com/problems/search-in-rotated-sorted-array-ii/)	| Medium	|
diff --git a/Stack/LargestRectangleInHistogram.swift b/Stack/LargestRectangleInHistogram.swift
new file mode 100644
index 00000000..e1607c5f
--- /dev/null
+++ b/Stack/LargestRectangleInHistogram.swift
@@ -0,0 +1,19 @@
+class Solution {
+    func largestRectangleArea(_ heights: [Int]) -> Int {
+        var heights = [heights, [0]].flatMap{ $0 }
+        var result = 0
+        var stacks = [Int]()
+        
+        for i in 0..<heights.count {
+            if !stacks.isEmpty && heights[i] < heights[stacks.last!] {
+                repeat {
+                    let val = stacks.popLast()!
+                    result = max(result, heights[val] * (stacks.isEmpty ? i : i-stacks.last!-1))
+                } while !stacks.isEmpty && heights[i] < heights[stacks.last!]
+            }
+            stacks.append(i)
+        }
+        
+        return result
+    }
+}
\ No newline at end of file
diff --git a/String/DetermineIfTwoStringsAreClose.swift b/String/DetermineIfTwoStringsAreClose.swift
new file mode 100644
index 00000000..9a5d20d3
--- /dev/null
+++ b/String/DetermineIfTwoStringsAreClose.swift
@@ -0,0 +1,9 @@
+class Solution {
+    func closeStrings(_ word1: String, _ word2: String) -> Bool {
+        var dic1 = Dictionary(grouping: Array(word1)) { $0 }
+        var dic2 = Dictionary(grouping: Array(word2)) { $0 }
+        
+        return dic1.map { $0.0 }.sorted() == dic2.map { $0.0 }.sorted()
+            && dic1.map { $1.count }.sorted() == dic2.map { $1.count }.sorted()
+    }
+}
\ No newline at end of file
diff --git a/String/FizzBuzz.swift b/String/FizzBuzz.swift
index 952f584d..438577b3 100644
--- a/String/FizzBuzz.swift
+++ b/String/FizzBuzz.swift
@@ -1,31 +1,22 @@
-/**
- * Question Link: https://leetcode.com/problems/fizz-buzz/
- * Primary idea: Iterate the array and handle multiples of 3 or 5 separately.
- *
- * Time Complexity: O(n), Space Complexity: O(1)
- *
- */
-
-class FizzBuzz {
+class Solution {
     func fizzBuzz(_ n: Int) -> [String] {
-        var res = [String]()
-    
-        if n < 0 {
-            return res
-        }
-        
-        for i in 1...n {
-            if i % 3 == 0 && i % 5 == 0 {
-                res.append("FizzBuzz")
-            } else if i % 3 == 0 {
-                res.append("Fizz")
-            } else if i % 5 == 0 {
-                res.append("Buzz")
-            } else {
-                res.append("\(i)")
+        var result = [String]()
+        for x in 1...n {
+            let m3 = x.isMultiple(of: 3)
+            let m5 = x.isMultiple(of: 5)
+            
+            switch (m3, m5) {
+                case (true, true):
+                result.append("FizzBuzz")
+                case (true, false):
+                result.append("Fizz")
+                case (false, true):
+                result.append("Buzz")
+                default:
+                result.append("\(x)")
             }
         }
         
-        return res
+        return result
     }
 }
\ No newline at end of file