LeetCode53. Maximum Subarray一種很好的做法

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:

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

注意點：
1. val的初值是nums[0]

2. 如果val < sum 則 val = sum;

3. 如果sum小於 0 則sum重置0，但這一步是在給val賦值之後。