3. Longest Substring Without Repeating Characters

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.


最长不含重复字符的子字符串

C++:

class Solution {
public:
    int lengthOfLongestSubstring(string s) {
        int curLen = 0 ;
        int maxLen = 0 ;
        vector<int> preIndex(256 , -1) ;
        for(int i = 0 ; i < s.length() ; i++){
            int pre = preIndex[s[i]] ;
            if (pre == -1 || i - pre > curLen){
                curLen++ ;
            }else{
                curLen = i - pre ;
            }
            preIndex[s[i]] = i ;
            if (curLen > maxLen){
                maxLen = curLen ;
            }
        }
        
        return maxLen ;
    }
};