   Type like pro

# All unique letter substring

## Problem

Given a string find out the longest substring which has all unique letters, i.e. no letter is repeated.

## Solution

We start by putting two pointers named startIndex and endIndex at the beginning of the string. As we move forward the end index new found letters are added in a set. If the letter is already found in the set, we start moving the start pointer and keep on removing the corresponding letters. When we found that the letter which caused the repetition is removed from the set, then we know that all the letters are unique in this substring. Every time we find such substrings we compare its length with a kept maximum. In this way we find the longest substring which does not have any repetition.

## Code

```import java.util.HashMap;
import java.util.HashSet;

public class AllUniqueSubstring
{
public static void main(String[] args)
{
printAllUniqueSubstring(input);
}

public static void printAllUniqueSubstring(String input)
{
HashSet<Character> set = new HashSet<Character>();
int startIndex = 0;
int endIndex = 0;
int maxLength = 0;
int startMax = 0;
int endMax = 0;

while (endIndex < input.length())
{
{
int currentLength = endIndex - startIndex + 1;
if (currentLength > maxLength)
{
maxLength = currentLength;
startMax = startIndex;
endMax = endIndex;
}
endIndex++;
} else
{
char removeChar = input.charAt(startIndex);
set.remove(removeChar);
startIndex++;
{
int currentLength = endIndex - startIndex + 1;
if (currentLength > maxLength)
{
maxLength = currentLength;
startMax = startIndex;
endMax = endIndex;
}
endIndex++;
}
}
}
System.out.println(startMax + "," + endMax);
System.out.println(input.substring(startMax, endMax));
}

}
```