(leetcode)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.

使用两个指针，start，end，当sum（start，end） < s时，就end++；

否则，将start前移知道找到第一个sum<s的start，并记录最小长度end-start，每次更新最小

 class Solution {
 public:
 // 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.
     int retmin(int a,int b)
     {
         return a<b?a:b;
     }
     int minSubArrayLen(int s, vector<int>& nums) {
         int start = ;
         int end = ;
         int sum = ;
         int min = INT_MAX;

         while(start<nums.size() && end<nums.size())
         {
             while(sum < s && end < nums.size()) sum+=nums[end++];
             while(sum >= s && start <= end)
             {
                 min = retmin(min,end-start);
                 sum -= nums[start++];
             }

         }
         return min==INT_MAX ?:min;
     }
 };