209 Minimum Size Subarray Sum

链接：https://leetcode.com/problems/minimum-size-subarray-sum/
问题描述：
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.

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

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Hide Similar Problems (H) Minimum Window Substring

给出数组和一个数字s，求数组中的一个最小区间，区间内的和大于等于s。总体思想和Minimum Window Substring 这一题相似。采用双指针的思想，计算p1和p2之间的和如果和小于s则p2++，如果大于等于s就更新最小值同时p1++。

class Solution {public:    int minSubArrayLen(int s, vector<int>& nums) {        int p1=0,p2=0,sum=0;        int min=INT_MAX;        while(p2<nums.size()||sum>s)        {          if(p1==p2)          {             sum=nums[p2++];             if(sum>=s)                 return 1;          }          else if(sum<s)              sum+=nums[p2++];          else if(sum>=s)          {           if(p2-p1<min)             min=p2-p1;           sum-=nums[p1++];          }        }        if(sum>=s&&p2-p1<min)          min=p2-p1;        if(min==INT_MAX)            return 0;        return  min;    }};