209. Minimum Size Subarray Sum

Given an array of n positive integers and a positive integer s, find the minimal length of a subarray of which the sum ≥ s. If there isn't one, return 0 instead.

For example, given the array [2,3,1,2,4,3] and s = 7,
the subarray [4,3] has the minimal length under the problem constraint.

click to show more practice.

Credits:
Special thanks to @Freezen for adding this problem and creating all test cases.

Subscribe to see which companies asked this question

分析：

1、不能对原序列排序。

2、从最0开始查，一直到最后，线性时间。

代码：

class Solution {
public:
    int minSubArrayLen(int s, vector<int>& nums) {
        int sum=0;
        int MIN=INT_MAX;
        int start=0;
        for(int i=0;i<nums.size();++i)
        {
            sum+=nums[i];
            while(sum>=s)
            {
                MIN=min(MIN,i-start+1);
                sum=sum-nums[start++];
            }
        }
        return MIN==INT_MAX?0:MIN;
    }
};