BAEL3455 Maximum Subarray Problem

algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/subarray/maximum/BruteForceAlgorithm.java

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+package com.baeldung.algorithms.subarray.maximum;
+
+public class BruteForceAlgorithm {
+
+    public int maxSubArray(int[] arr) {
+
+        int size = arr.length;
+        int maximumSubArraySum = Integer.MIN_VALUE;
+        int start = 0;
+        int end = 0;
+
+        for (int left = 0; left < size; left++) {
+
+            int runningWindowSum = 0;
+
+            for (int right = left; right < size; right++) {
+                runningWindowSum += arr[right];
+
+                if (runningWindowSum > maximumSubArraySum) {
+                    maximumSubArraySum = runningWindowSum;
+                    start = left;
+                    end = right;
+                }
+            }
+        }
+        System.out.println("Found Maximum Subarray between " + start + " and " + end);
+        return maximumSubArraySum;
+    }
+
+}

algorithms-miscellaneous-5/src/main/java/com/baeldung/algorithms/subarray/maximum/KadaneAlgorithm.java

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+package com.baeldung.algorithms.subarray.maximum;
+
+public class KadaneAlgorithm {
+
+    public int maxSubArraySum(int[] arr) {
+
+        int size = arr.length;
+        int start = 0;
+        int end = 0;
+
+        int maxSoFar = 0, maxEndingHere = 0;
+
+        for (int i = 0; i < size; i++) {
+
+            if (arr[i] > maxEndingHere + arr[i]) {
+                start = i;
+                maxEndingHere = arr[i];
+            } else
+                maxEndingHere = maxEndingHere + arr[i];
+
+            if (maxSoFar < maxEndingHere) {
+                maxSoFar = maxEndingHere;
+                end = i;
+            }
+        }
+        System.out.println("Found Maximum Subarray between " + start + " and " + end);
+        return maxSoFar;
+    }
+}

algorithms-miscellaneous-5/src/test/java/com/baeldung/algorithms/subarray/maximum/BruteForceAlgorithmUnitTest.java

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+package com.baeldung.algorithms.subarray.maximum;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+class BruteForceAlgorithmUnitTest {
+
+    @Test
+    void givenArrayWithNegativeNumberWhenMaximumSubarrayThenReturns6() {
+        //given
+        int[] arr = new int[]{-3, 1, -8, 4, -1, 2, 1, -5, 5};
+
+        //when
+        BruteForceAlgorithm algorithm = new BruteForceAlgorithm();
+        int maximumSum = algorithm.maxSubArray(arr);
+
+        //then
+        assertEquals(6, maximumSum);
+
+    }
+
+}

algorithms-miscellaneous-5/src/test/java/com/baeldung/algorithms/subarray/maximum/KadaneAlgorithmUnitTest.java

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+package com.baeldung.algorithms.subarray.maximum;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class KadaneAlgorithmUnitTest {
+
+    @Test
+    void givenArrayWithNegativeNumberWhenMaximumSubarrayThenReturns6() {
+        //given
+        int[] arr = new int[]{-3, 1, -8, 4, -1, 2, 1, -5, 5};
+
+        //when
+        KadaneAlgorithm algorithm = new KadaneAlgorithm();
+        int maxSum = algorithm.maxSubArraySum(arr);
+
+        //then
+        assertEquals(6, maxSum);
+
+    }
+
+}