leetcode 第209题 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.

C++代码实现：

class Solution {public:    int minSubArrayLen(int s, vector<int>& nums) {        int firstpos = 0; //最小子序列首位置        int sum = 0;        int minlen = INT_MAX;        for(int i = 0; i < nums.size();++i){            sum += nums[i];            while(sum >= s){                minlen = min(minlen,i - firstpos + 1);                sum -= nums[firstpos];                firstpos++;            }        }        return minlen == INT_MAX?0:minlen;    }};