53. Maximum Subarray(补上周)

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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这题是一道经典的dp问题，我们可以很容易的得到其dp方程，假设dp[i]是数组a [0, i]区间最大的值，那么
dp[i + 1] = max(dp[i], dp[i] + a[i + 1])

代码如下:

class Solution {
public:
    int maxSubArray(vector<int>& nums) {
        int sum = 0;
        int n=nums.size();
        int m = INT_MIN;
        for(int i = 0; i < n; i++) {
        sum += nums[i];
        m = max(m, sum);
        //如果sum小于0了，将sum重置为0，从i + 1再次开始计算
        if(sum < 0) {
        sum = 0;
            }
        }
        return m;
    }
};