Minimum Size Subarray Sum*

LeetCode 209

class Solution:
    def minSubArrayLen(self, s, nums):
        """
        :type s: int
        :type nums: List[int]
        :rtype: int
        """
        """
        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.
        
        Kandane's Algorithm
        i 與 j 在同一個位置 然後 j 一直往前找並且累加值直到 curSum "大於" 所求值
        (不是大於等於喔 因為題目要求 sum ≥ s) 
        然後當前值減去 num[i] 然後 i 往前移
        """
        i = j = curSum = 0
        mini = math.inf
        
        while j < len(nums):

            if curSum + nums[j] < s:
                curSum = curSum + nums[j]
                j += 1
            else:
                mini = min(j-i+1, mini)
                curSum = curSum - nums[i]                   
                i += 1
                                          
        return mini if mini != math.inf else 0