# 209. Longest Substring Without Repeating Characters

# 題目 LeetCode 209

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

# 解題思路

題目：給一組陣列和 target 數，如果陣列的值連續相加超過 target 則回傳長度，長度最小者為答案。

• 定義開始、結束、總和皆為 0。先預設最小長度為無限（Infinity），因為需要讓長度做比較回傳。
• 開始位置加總直到總和 sum 大於 target 後進入判斷當前窗口大小再存放至 minLength 中
• 回傳長度

補充：

1. Infinity

# 程式

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• Time Complexity: O(n)
• Space Complexity: O(1)