leetcode 53. Maximum Subarray(DP動態規劃問題)

問題描述：

  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.

思路：

  本題為最優解問題，可利用動態規劃思路求解。從頭到尾遍曆每一個數組元素，如何前面元素的和為正，則加上本元素的值繼續搜尋；如何前面元素的和為負，則此元素開始新的和計數。整個過程中要注意更新和的最大值。

代碼：

class Solution {    public int maxSubArray(int[] nums) {        if(nums == null) return 0;        int sum = 0;        int max = Integer.MIN_VALUE;        for(int i = 0 ; i < nums.length; i++){            if(sum + nums[i] > nums[i])                sum += nums[i];            else                sum = nums[i];            if(sum > max)                max = sum;        }        return max;           }}