minimum-size-subarray-sum.cpp

// Given an array of n positive integers and a positive integer s, find the minimal length of a contiguous subarray of which the sum ≥ s. If there isn't one, return 0 instead.
//
// Example: 
//
//
// Input: s = 7, nums = [2,3,1,2,4,3]
// Output: 2
// Explanation: the subarray [4,3] has the minimal length under the problem constraint.
//
// Follow up:
//
// If you have figured out the O(n) solution, try coding another solution of which the time complexity is O(n log n). 
//


class Solution {
public:
    int minSubArrayLen(int s, vector<int>& nums) {
        int start = 0, current = 0, sum = 0, ans = INT_MAX;
        while (current < nums.size()) {
            sum += nums[current++];

            while (sum >= s) {
                ans = min(ans, current-start);
                sum -= nums[start++];
            }
        }
        return ans==INT_MAX ? 0 : ans;
    }
};