209. 长度最小的子数组

 1 //跟LeetCode3类似
 2 class Solution 
 3 {
 4 public:
 5     int minSubArrayLen(int s, vector<int>& nums) 
 6     {
 7         //如果为空,直接返回0
 8         if(nums.empty()) return 0;
 9         int res = 0;
10         for(auto a : nums) res += a;
11         //如果数组总和小于s,直接返回0
12         if(res < s) return 0;
13 
14         res = 0;
15         int len = INT_MAX;
16         int n = nums.size();
17         int begin = 0;
18         for(int i = 0;i < n;i ++)
19         {   
20             res += nums[i];
21             while(res >= s)
22             {
23                 len = min(len,i - begin + 1);
24                 res -= nums[begin++];
25             }
26         }
27         len = min(len,n - begin + 1);
28         return len;
29     }
30 };