面试经典150题——Day31

一、题目

3. Longest Substring Without Repeating Characters

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 * 104
s consists of English letters, digits, symbols and spaces.

题目来源： leetcode

二、题解

双指针+滑动窗口

class Solution {
public:
    int lengthOfLongestSubstring(string s) {
        int n = s.length();
        if(n == 0) return 0;
        int i = 0;
        unordered_map<char,int> map;
        map[s[i]] = 1;
        int res = 1;
        for(int j = 1;j < n;j++){
            while(map[s[j]] == 1 && i < j){
                map[s[i]] = 0;
                i++;
            }
            if(map[s[j]] != 1) map[s[j]] = 1;
            res = max(res,j - i + 1);
        }
        return res;
    }
};