Swift LeetCode SlideWindow

209. Minimum Size Subarray Sum

Given an array of positive integers nums and a positive integer target, return the minimal length of a contiguous subarray [numsl, numsl+1, ..., numsr-1, numsr] of which the 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 <= 109
• 1 <= nums.length <= 105
• 1 <= nums[i] <= 105

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)).

Question

class Solution {
 func minSubArrayLen(_ target: Int, _ nums: [Int]) -> Int {
 }
}

Solution

func minSubArrayLen(_ target: Int, _ nums: [Int]) -> Int {
   var windowSum = 0, windowStart = 0
   var minWindowSize = Int.max
   for windowEnd in 0..<nums.count{
   windowSum += nums[windowEnd]
   while (windowSum >= target) {
     minWindowSize = min(minWindowSize, windowEnd - windowStart + 1)
     windowSum -= nums[windowStart]
     windowStart += 1
   }
  } 
return minWindowSize == Int.max ? 0 : minWindowSize
}

More: https://www.youtube.com/watch?v=7Q1uylXOatU