Given a string s, find the length of the longest substring
without repeating characters.
Example 1:
Input: s = "abcabcbb"
Output: 3
Explanation: The answer is "abc", with the length of 3.
Example 2:
Input: s = "bbbbb"
Output: 1
Explanation: The answer is "b", with the length of 1.
Example 3:
Input: s = "pwwkew"
Output: 3
Explanation: The answer is "wke", with the length of 3.
Notice that the answer must be a substring, "pwke" is a subsequence and not a substring.
Constraints:
0 <= s.length <= 5 * 104s consists of English letters, digits, symbols and spaces.給定一個字串 s
要求寫一個演算法找出子字串中不包含重複字元的最長長度
最直接的想法是
當還沒遇到重複字元時就累加長度。遇到重複字元時，就從上一次開始累加的位置start 右移一位， 也就是start+1 當作下一個開始做累計
