Print all Possible Characters

Implement a method to generate all possible combinations given a string input.

The method has other parameters:


StringBuffer outstr = new StringBuffer();
List arr = new ArrayList(); 
int index: is start index : 0;

combine("abc",out,0,arr) --> {a,ab,abc,ac,b,bc,c}

Need a hand? Try out these hints, one at a time.

The key here is to use recursive calls to display combination of characters by appending each a Character at each step.

Each loop iteration proceeds as follows:

1. Append a Character

2. Print the result

3. Perform a recursive invocation at the level i+1

4. Remove the Character we added at step 1.

public static List<String> combine(String instr, StringBuffer outstr, int index, List<String> arr) {
    

    

}

Java

Python