Maximum Subarray

Change-Id: I9b3057c4080dcaae52da93db46900274b3b0f0b0

Author: applewjg

MaximumSubarray.java

@@ -0,0 +1,33 @@
+/*
+ Author:     King, [email protected]
+ Date:       Dec 25, 2014
+ Problem:    Maximum Subarray
+ Difficulty: Medium
+ Source:     https://oj.leetcode.com/problems/maximum-subarray/
+
+ Find the contiguous subarray within an array (containing at least one number) which has the largest sum.
+ For example, given the array [-2,1,-3,4,-1,2,1,-5,4], the contiguous subarray [4,-1,2,1] has the largest sum = 6.
+
+ Solution: dp.
+ */
+public class Solution {
+    public int maxSubArray_1(int[] A) {
+        if (A.length == 0) return 0;
+        int minVal = Math.min(A[0],0), res = A[0], sum = A[0];
+        for (int i = 1; i < A.length; ++i) {
+            sum += A[i];
+            res = Math.max(res, sum - minVal);
+            minVal = Math.min(minVal, sum);
+        }
+        return res;
+    }
+    public int maxSubArray_2(int[] A) {
+        if (A.length == 0) return 0;
+        int dp = A[0], res = A[0];
+        for (int i = 1; i < A.length; ++i) {
+            dp = Math.max(A[i], dp + A[i]);
+            res = Math.max(res, dp);
+        }
+        return res;
+    }
+}