Add code to find max of sub array

Author: jbee37142

src/test/java/exercise/FindMaxSumInArray.java

@@ -0,0 +1,42 @@
+package exercise;
+
+import org.junit.Test;
+
+import static org.hamcrest.CoreMatchers.is;
+import static org.junit.Assert.assertThat;
+
+public class FindMaxSumInArray {
+
+    /*
+        TASK
+        주어진 배열에서 합이 최대가 되는 sub array의 합을 구한다.
+     */
+
+    @Test
+    public void test() {
+        int[] arr1 = {1,2,-9,4,-3,12,24,3,4,-8,10,9};
+        assertThat(solution(arr1), is(55));
+        int[] arr2 = {};
+        assertThat(solution(arr2), is(Integer.MAX_VALUE));
+        int[] arr3 = {1};
+        assertThat(solution(arr3), is(1));
+        int[] arr4 = {1,2};
+        assertThat(solution(arr4), is(3));
+    }
+
+    public int solution(int[] arr) {
+        if (arr == null || arr.length == 0) return Integer.MAX_VALUE;
+
+        int max = arr[0];
+
+        for (int i = 1; i < arr.length; i++) {
+            if (arr[i] > max + arr[i]) {
+                max = arr[i];
+            } else {
+                max += arr[i];
+            }
+        }
+
+        return max;
+    }
+}