```
hopefully this helps.
public class Solution {
public int lengthOfLongestSubstring(String s) {
if (s.length()<=1) return s.length();
int[] table = new int[256];
int slow=0;
int fast=1;
table[s.charAt(slow)]=1;
int max=0;
while(fast<s.length()){
if(table[s.charAt(fast)]==1){
slow++;
table[s.charAt(slow-1)]=0;
}
else{
fast++;
table[s.charAt(fast-1)]=1;
}
if(max<fast-slow) max=fast-slow;
}
return max;
}
}
```

I was going to use a hashtable then realized I don't need it. Realized I could use a Boolean array instead