Minimum Size Subarray Sum - LeetCode : Swift

Minimum Size Subarray Sum - LeetCode

Given an array of positive integers nums and a positive integer target, return the minimal length of a subarray whose sum is greater than or equal to target. If there is no such subarray, return 0 instead.

Example 1:

Input: target = 7, nums = [2,3,1,2,4,3]
Output: 2
Explanation: The subarray [4,3] has the minimal length under the problem constraint.

Example 2:

Input: target = 4, nums = [1,4,4]
Output: 1

Example 3:

Input: target = 11, nums = [1,1,1,1,1,1,1,1]
Output: 0

Constraints:

• 1 <= target <= 10^9
• 1 <= nums.length <= 10^5
• 1 <= nums[i] <= 10^4

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 {
    func minSubArrayLen(_ target: Int, _ nums: [Int]) -> Int {
        var ans = Int.max , sum = 0, low = 0

        for i in 0..<nums.count {
            sum += nums[i]
   
                while (sum >= target) {
                    ans = min(ans, i - low + 1)
                    sum -= nums[low]
                    low += 1
                }
                    
        }
        return ans == Int.max ? 0 : ans
    }
}