https://leetcode.com/problems/jump-game/

interview_prep/algorithm/java/src/main/java/hoa/can/code/ez/PartitionEqualSubSetSum.java

@@ -1,7 +1,5 @@
 package hoa.can.code.ez;
 
-import java.util.Arrays;
-
 import util.Array;
 
 public class PartitionEqualSubSetSum {
@@ -12,7 +10,6 @@ public static int equalPartition(int n, int arr[]){
     }
 
     static int canAddUp(int arr[], int target){
-        System.out.println(String.format("canAddUp %d %s", target, Arrays.toString(arr)));
         if(target==0){
             return 1;
         }

interview_prep/algorithm/java/src/main/java/hoa/can/code/gg/JumpingDP.java

@@ -0,0 +1,31 @@
+package hoa.can.code.gg;
+
+public class JumpingDP {
+    public static boolean canJump(int[] nums) {
+        return minJumps(nums) != Integer.MAX_VALUE;
+    }
+
+    public static int minJumps(int[] arr) {
+        int n = arr.length;
+        int minCostToIdx[] = new int[n];
+        // result
+        int i, j;
+
+        // if first element is 0,
+        if (n == 0 || arr[0] == 0)
+            return Integer.MAX_VALUE;
+
+        minCostToIdx[0] = 0;
+
+        for (i = 1; i < n; i++) {
+            minCostToIdx[i] = Integer.MAX_VALUE;
+            for (j = 0; j < i; j++) {
+                if (i <= j + arr[j] && minCostToIdx[j] != Integer.MAX_VALUE) {
+                    minCostToIdx[i] = Math.min(minCostToIdx[i], minCostToIdx[j] + 1);
+                    break;
+                }
+            }
+        }
+        return minCostToIdx[n - 1];
+    }
+}

interview_prep/algorithm/java/src/main/java/hoa/can/code/gg/JumpingGreedily.java

@@ -0,0 +1,44 @@
+package hoa.can.code.gg;
+
+public class JumpingGreedily {
+    final static int NO_WAY = 10000;
+
+    public static boolean canJump(int[] nums) {
+        return minJumps(nums) != NO_WAY;
+    }
+
+    public static int minJumps(int[] nums) {
+        int n = nums.length;
+        if (n <= 1) {
+            return 0;
+        }
+
+        int maxReach = nums[0];
+        int currentMax = nums[0];
+
+        if (currentMax == 0) return NO_WAY;
+        if (currentMax >= n - 1) return 1;
+
+        int steps = 1;
+
+        for (int currentBase = 1; currentBase < n; currentBase++) {
+            if (currentBase > maxReach) {
+                steps++;
+                maxReach = currentMax;
+                if (currentMax >= n - 1) return steps;
+            }
+            if (nums[currentBase] == 0) {
+                if ((currentMax == currentBase)) {
+                    return NO_WAY;
+                }
+                if (currentMax >= n - 1) {
+                    steps++;
+                    return steps;
+                }
+            }
+
+            currentMax = Math.max(currentMax, currentBase + nums[currentBase]);
+        }
+        return steps;
+    }
+}

interview_prep/algorithm/java/src/main/java/hoa/can/code/gg/JumpingRecursive.java

@@ -0,0 +1,37 @@
+package hoa.can.code.gg;
+
+import java.util.Arrays;
+
+/**
+ * <a href="https://leetcode.com/problems/jump-game/">Desc</a>
+ */
+public class JumpingRecursive {
+    final static int NO_WAY = 10000;
+
+    public static boolean canJump(int[] nums) {
+        int step = minJumps(nums);
+        return (step != NO_WAY);
+    }
+
+    public static int minJumps(int[] nums) {
+        int[] memo = new int[nums.length];
+        Arrays.fill(memo, -1);
+        int lastIdx = nums.length - 1;
+        return minJumps(nums, 0, lastIdx, memo);
+    }
+
+    private static int minJumps(int[] steps, int begin, int dest, int[] memo) {
+        if (begin == dest)
+            return 0;
+        if (steps[begin] == 0)
+            return NO_WAY;
+
+        int minJump = NO_WAY;
+        for (int step = steps[begin]; step >= 1; --step) {
+            if (begin + step <= dest) {
+                minJump = Math.min(minJump, 1 + minJumps(steps, begin + step, dest, memo));
+            }
+        }
+        return memo[begin] = minJump;
+    }
+}

interview_prep/algorithm/java/src/test/java/hoa/can/code/JumpingTest.java

@@ -0,0 +1,93 @@
+package hoa.can.code;
+
+import hoa.can.code.gg.JumpingDP;
+import hoa.can.code.gg.JumpingGreedily;
+import hoa.can.code.gg.JumpingRecursive;
+import org.junit.jupiter.api.Disabled;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+import java.util.Arrays;
+
+import static java.lang.String.format;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+public class JumpingTest {
+    @Test
+    @DisplayName("ok")
+    public void yes() {
+        //canJump(new int[]{0});// depends
+        canJump(new int[]{2, 3, 1, 1, 4});
+        canJump(new int[]{1, 3, 5, 8, 9, 2, 6, 7, 6, 8, 9});
+        canJump(new int[]{3, 2, 1, 1, 1, 2, 3, 4, 5, 1, 3, 0, 2, 3, 0, 3, 1, 2, 3, 9, 1, 0, 0, 4, 1, 1, 1, 0, 2, 3, 4, 0, 9, 0, 0, 1, 2, 3, 9, 0, 0, 1, 0, 0, 1, 0, 1, 2, 3, 4});
+    }
+
+    @Test
+    @DisplayName("nope")
+    public void no() {
+        canNotJump(new int[]{0, 1});
+        canNotJump(new int[]{3, 2, 1, 0, 4});
+        canNotJump(new int[]{2, 0, 0, 0, 3});
+        canNotJump(new int[]{4, 3, 2, 1, 0, 0, 0});
+        canNotJump(new int[]{3, 2, 1, 0, 1, 2, 3, 4, 5, 1, 0, 0, 2, 3, 0, 0, 1, 2, 3, 0, 1, 0, 0, 4, 1, 1, 1, 0, 2, 3, 4, 0, 0, 0, 0, 1, 2, 3, 4, 0, 0, 1, 0, 0, 1, 0, 1, 2, 3, 4});
+    }
+
+    @Test
+    @DisplayName("yes-WithDetail")
+    public void yesWithDetail() {
+        yesWithDetail(new int[]{1, 2}, 1, "1 -> end");
+        yesWithDetail(new int[]{2,0,1},1, "2 -> end");
+        yesWithDetail(new int[]{2, 3, 1, 1, 4}, 2, "2 -> 3 -> end");
+        yesWithDetail(new int[]{10, 8, 12, 17, 1, 21, 5, 17, 20, 11, 5, 27, 23, 8, 12, 18, 16, 12, 9, 8, 17, 12, 23, 26, 0, 5, 9, 24, 10}, 2, "10 -> 20 -> end");
+        yesWithDetail(new int[]{5, 9, 3, 2, 1, 0, 2, 3, 3, 1, 0, 0}, 3, "5->9->3->end");
+        yesWithDetail(new int[]{1, 1, 1, 1, 1, 1}, 5, "1 -> 1 ->... end");
+    }
+
+    @Test
+    @DisplayName("nope")
+    @Disabled("TOO SLOW TO CHECK ALL COMBINATIONS")
+    public void nope() {
+        assertEquals(
+                13,
+                JumpingRecursive.minJumps(new int[]{8, 2, 4, 4, 4, 9, 5, 2, 5, 8, 8, 0, 8, 6, 9, 1, 1, 6, 3, 5, 1, 2, 6, 6, 0, 4, 8, 6, 0, 3, 2, 8, 7, 6, 5, 1, 7, 0, 3, 4, 8, 3, 5, 9, 0, 4, 0, 1, 0, 5, 9, 2, 0, 7, 0, 2, 1, 0, 8, 2, 5, 1, 2, 3, 9, 7, 4, 7, 0, 0, 1, 8, 5, 6, 7, 5, 1, 9, 9, 3, 5, 0, 7, 5}),
+                "quick"
+        );
+    }
+
+    @Test
+    @DisplayName("yep")
+    public void yep() {
+        assertEquals(
+                13,
+                JumpingGreedily.minJumps(new int[]{8,2,4,4,4,9,5,2,5,8,8,0,8,6,9,1,1,6,3,5,1,2,6,6,0,4,8,6,0,3,2,8,7,6,5,1,7,0,3,4,8,3,5,9,0,4,0,1,0,5,9,2,0,7,0,2,1,0,8,2,5,1,2,3,9,7,4,7,0,0,1,8,5,6,7,5,1,9,9,3,5,0,7,5}),
+                "quick"
+        );
+        assertEquals(
+                13,
+                JumpingDP.minJumps(new int[]{8, 2, 4, 4, 4, 9, 5, 2, 5, 8, 8, 0, 8, 6, 9, 1, 1, 6, 3, 5, 1, 2, 6, 6, 0, 4, 8, 6, 0, 3, 2, 8, 7, 6, 5, 1, 7, 0, 3, 4, 8, 3, 5, 9, 0, 4, 0, 1, 0, 5, 9, 2, 0, 7, 0, 2, 1, 0, 8, 2, 5, 1, 2, 3, 9, 7, 4, 7, 0, 0, 1, 8, 5, 6, 7, 5, 1, 9, 9, 3, 5, 0, 7, 5}),
+                "quick"
+        );
+    }
+
+    void canJump(int[] steps) {
+        String log = format("%s Should be REACHABLE", Arrays.toString(steps));
+        assertTrue(JumpingRecursive.canJump(steps), log);
+        assertTrue(JumpingGreedily.canJump(steps), log);
+        assertTrue(JumpingDP.canJump(steps), log);
+    }
+
+    void canNotJump(int[] steps) {
+        assertFalse(JumpingRecursive.canJump(steps));
+        assertFalse(JumpingGreedily.canJump(steps));
+        assertFalse(JumpingDP.canJump(steps));
+    }
+
+    void yesWithDetail(int[] steps, int expected, String msg) {
+        String log = format("\n%s \n%s", Arrays.toString(steps), msg);
+        assertEquals(expected, JumpingRecursive.minJumps(steps), log);
+        assertEquals(expected, JumpingGreedily.minJumps(steps), log);
+        assertEquals(expected, JumpingDP.minJumps(steps), log);
+    }
+}

interview_prep/algorithm/java/src/test/java/hoa/can/PartitionEqualSubSetSumTest.java → interview_prep/algorithm/java/src/test/java/hoa/can/code/PartitionEqualSubSetSumTest.java

@@ -1,4 +1,4 @@
-package hoa.can;
+package hoa.can.code;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;