3. Longest Substring Without Repeating Characters

题目

Given a string, find the length of the longest substring without repeating characters.

Example 1:

Input: "abcabcbb"
Output: 3 
Explanation: The answer is "abc", with the length of 3.

Example 2:

Input: "bbbbb"
Output: 1
Explanation: The answer is "b", with the length of 1.

Example 3:

Input: "pwwkew"
Output: 3
Explanation: The answer is "wke", with the length of 3. 
             Note that the answer must be a substring, "pwke" is a subsequence and not a substring.

题目大意

在一个字符串重寻找没有重复字母的最长子串。

解题思路

这一题和第 438 题，第 3 题，第 76 题，第 567 题类似，用的思想都是"滑动窗口"。

滑动窗口的右边界不断的右移，只要没有重复的字符，就不用的向右扩大窗口边界。一旦出现了重复字符，此时先计算一下滑动窗口的大小，记录下来。再需要缩小左边界。直到重复的字符移出了左边界。接着又可以开始移动滑动窗口的右边界。以此类推，不断的刷新记录的窗口大小。最终最大的值就是题目中的所求。