// Source : https://leetcode.com/problems/minimum-size-subarray-sum/

// Author : weekend27

// Date : 2015-12-03

/**********************************************************************************

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.

**********************************************************************************/

// How to do it:

// two pointers, sliding window

class Solution {

public:

int minSubArrayLen(int s, vector<int>& nums) {

int len = nums.size();

if (len == 0)

return 0;

int minLen = len + 1;

int start = 0, end = 0, sum = 0;

while(end < len){

while(sum < s && end < len){

sum += nums[end];

end++;

}

while(sum >= s && start < len){

minLen = min(minLen, end-start);

if (minLen == 1)

return minLen;

sum -= nums[start];

start++;

}

if (sum >= s)

minLen = min(minLen, end-start);

}

return minLen == (len + 1) ? 0 : minLen;

}

};