209. Minimum Size Subarray Sum

• Difficulty: Medium

• Topics: Array, Two Pointers, Binary Search

• Similar Questions:

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  • Maximum Size Subarray Sum Equals k

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Problem:

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.

Solutions:

class Solution {
public:
    int minSubArrayLen(int s, vector<int>& nums) {
        int sum = 0;
        int left = 0;
        int len = INT_MAX;

        for (int right = 0; right < nums.size(); ++right) {
            sum += nums[right];

            while (left <= right && sum >= s) {
                len = min(len, right - left + 1);
                sum -= nums[left];
                ++left;
            }

        }

        return len == INT_MAX ? 0 : len;
    }
};