209_Minimum_Size_Subarray_Sum.py

"""
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
"""

class Solution:
    def minSubArrayLen(self, target: int, nums: List[int]) -> int:
        currentSum = 0
        minWindowLength = float('inf')

        #2pointes sliding window
        low = 0
        high = 0
        while high < len(nums):
            currentSum += nums[high]
            high += 1

            while currentSum >= target:
                currentWindowSize = high - low
                minWindowLength = min(minWindowLength , currentWindowSize)

                currentSum -= nums[low]
                low += 1

        return 0 if minWindowLength == float('inf') else minWindowLength