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by Sumit Chourasia | Nov 18, 2020 | Category :coding | Tags : algorithm array data-structure leetcode medium

Minimum Size Subarray Sum - Array - Medium - LeetCode

Minimum Size Subarray Sum - Array - Medium - LeetCode

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). 

public class Solution {
    public int MinSubArrayLen(int s, int[] nums) {
        if (nums.Length == 0)
            {
                return 0;
            }

            int start = 0;
            int end = 0;
            int sum = nums[0];
            int min = int.MaxValue;
            while (true)
            {
                if (sum >= s)
                {
                    if (end - start+1 < min)
                    {
                        min = end - start+1;
                    }
                    sum -= nums[start];
                    start++;
                }
                else
                {
                    end++;
                    if(end > nums.Length - 1)
                    {
                        break;
                    }
                    sum += nums[end];                    
                }
            }

            return min == int.MaxValue ? 0 : min;
    }
}

Time Complexity: O(n)

Space Complexity: O(1)