leetcode Minimum Size Subarray Sum 双指针

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.

题目意思是求大于给定数的子串和的最小长度。

可以用双指针做，类似滑动窗口。

定义一个left指针一个right指针，开始都指向头，然后如果sum<s则right不断向右，sum不断增大，然后left不断向右，sum不断减小，直到小于s。

class Solution {public://定义两个指针，一个左指针，一个右指针，开始都指向头，然后右指针向后直到满足条件，记录长度，则left向后一位，重复int minSubArrayLen(int s, vector<int>& nums) {if (!nums.size()) return 0;int sum = 0;int left = 0, right = 0,size=nums.size();int mincount = size;bool flag = false;while (right<size){while (right<size&&sum<s){sum += nums[right++];}while(sum>=s)//满足条件{mincount = min(right - left,mincount);flag = true;sum -= nums[left++];}}if (flag) return mincount;return 0;}};