CareerCup

This is the one when we don't know the lenght.

public String recursiveReverseString(String s) {
if (s.length() <= 1)
return s;
else
return recursiveReverseString(s.substring(1)) + s.charAt(0);
}

Is this C style null terminated string ?
Please clarify the question.

a string is always ended by '/0' we can use this end of string character to reverse string.

Add it to the string buffer and use reverse function in java

@pedro
Why dont you make a new string and than iterate the original string and start inserting characters in the beginning of new string.
It would be better.

And finding sub string also requires the length of string.
And its also O(n)

I guess we need to do it in place.

char token;
int temp=0;
int i;

while(str[temp]!='\0')
{
token = str[temp+1];

use a stack, keep pushing until you encounter a '\0'. once there pop until the stack is empty and overwrite the original string (if you dont need it)