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.

cclass Solution {
public:
    int minSubArrayLen(int s, vector<int>& nums) {
        if(nums.size()<=0) return 0;
        int minlen=nums.size()+1,sum=nums[0],first=0,second=0;
        while(first<=second)
        {
            if(sum>=s)
            {
                if(second-first+1<minlen) minlen=second-first+1;
                sum-=nums[first];
                first++;
            }
            else
            {
                second++;
                if(second<nums.size())
                    sum+=nums[second];
                else
                    break;
            }
        }
        if(minlen!=nums.size()+1)
            return minlen;
        else
            return 0;
    }
};