fix the initial maxSum and add test

Author: sk1418

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

@@ -13,22 +13,22 @@ public int maxSubArraySum(int[] arr) {
         int start = 0;
         int end = 0;
 
-        int maxSoFar = 0, maxEndingHere = 0;
-
+        int maxSoFar = arr[0], maxEndingHere = arr[0];
         for (int i = 0; i < size; i++) {
 
             if (arr[i] > maxEndingHere + arr[i]) {
                 start = i;
                 maxEndingHere = arr[i];
-            } else
+            } else {
                 maxEndingHere = maxEndingHere + arr[i];
+            }
 
             if (maxSoFar < maxEndingHere) {
                 maxSoFar = maxEndingHere;
                 end = i;
             }
         }
-        logger.info("Found Maximum Subarray between {} and {}", start, end);
+        logger.info("Found Maximum Subarray between {} and {}", Math.min(start, end), end);
         return maxSoFar;
     }
 }

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

@@ -9,11 +9,22 @@ class KadaneAlgorithmUnitTest {
     @Test
     void givenArrayWithNegativeNumberWhenMaximumSubarrayThenReturns6() {
         //given
-        int[] arr = new int[]{-3, 1, -8, 4, -1, 2, 1, -5, 5};
+        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);
     }
+
+    @Test
+    void givenArrayWithAllNegativeNumbersWhenMaximumSubarrayThenReturnsExpectedResult() {
+        //given
+        int[] arr = new int[] { -8, -7, -5, -4, -3, -1, -2 };
+        //when
+        KadaneAlgorithm algorithm = new KadaneAlgorithm();
+        int maxSum = algorithm.maxSubArraySum(arr);
+        //then
+        assertEquals(-1, maxSum);
+    }
 }