209. Minimum Size Subarray Sum

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

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.

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).

Solution

class Solution {
public:
    int minSubArrayLen(int s, vector<int>& nums) {
        int sum = 0;
        int count = INT_MAX;
        int j = 0;
        for (int i = 0; i < nums.size(); ++i) {
            sum += nums[i];
            while (sum >= s) {
                count = min(count, i - j);
                sum -= nums[j++];
            }
        }
        return (count == INT_MAX) ? 0 : count + 1;
    }
};

• #twopointer

• #subarray