leetcode_53. Maximum Subarray

题目：

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.

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有一个思想是：如果这个子串大于零，可以继续往后加，因为加上他一定比不加它大。

于是就很简单了：

class Solution {public:    int maxSubArray(vector<int>& nums) {        int sum = nums[0], tsum = nums[0];        for(int i = 1; i < nums.size(); ++i){            if(tsum >= 0){                tsum += nums[i];            }            else{                tsum = nums[i];            }            if(sum < tsum){                sum = tsum;            }        }        return sum;    }};