000209-Minimum-Size-Subarray-Sum

Problem

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

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 <= 109 1 <= nums.length <= 105 1 <= nums[i] <= 104

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:
   def minSubArrayLen(self, target: int, nums: List[int]) -> int:
       left, right = 0, 0
       sub_sum, min_len = 0, float('inf')
       while right < len(nums):
           sub_sum += nums[right]

           while sub_sum >= target:
               min_len = min(min_len, right-left+1)
               sub_sum -= nums[left]
               left += 1
           right += 1
       
       if min_len == float('inf'):
           return 0
       return min_len