Longest Substring Without Repeating Characters.cpp

class Solution {
public:
    int lengthOfLongestSubstring(string s) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
     int length=s.length(); 
     bool exist[256]={false};
     int start=0; 
     int maxL=0; 
     for(int i=0; i<length; i++)
     {
         if(exist[s[i]])
         {
             maxL=max(maxL, i-start); 
             while(s[start]!=s[i])
             {
                exist[s[start]]=false;
                start++; 
             }
             start++;
         }else
         {
             exist[s[i]]=true;      
         }
     }
     return max(maxL, length-start); 
        
    }
};

Longest Substring Without Repeating Characters.java

public class Solution {
    public int lengthOfLongestSubstring(String s) {
        // Start typing your Java solution below
        // DO NOT write main() function
        int length=s.length(); 
        boolean [] exists=new boolean [256]; 
        int start=0, max=0; 
        for(int i=0; i<length; i++)
        {
            if(!exists[s.charAt(i)]) 
            {
                exists[s.charAt(i)]=true; 
            }else
            {
                max=Math.max(max, i-start);
                while(s.charAt(start)!=s.charAt(i))
                {
                    exists[s.charAt(start)]=false; start++; 
                }
                start++; 
            }
        }
        max=Math.max(max, length-start);
        return max; 
    }
}