leetcode209 Minimum Size Subarray Sum

"""
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.
Example:
Input: s = 7, nums = [2,3,1,2,4,3]
Output: 2
Explanation: the subarray [4,3] has the minimal length under the problem constraint.
"""
"""
滑动窗口，与leetcode713类似
"""
class Solution:
    def minSubArrayLen(self, s: int, nums):
        _sum = 0
        res = len(nums) + 1
        i = 0
        for j in range(len(nums)):
            _sum += nums[j]
            while _sum >= s: #！！！
                res = min(res, j-i+1)
                _sum -= nums[i]
                i += 1
        return res if res <= len(nums) else 0