WAP to generate the Dyck Word from given string.??

A Dyck word is a string consisting of n X's and n Y's such that no initial segment of the string has more Y's than X's

It Can Be Solved by Catalan Number Cn=2nCn/(n+1)=2n!/n!*n+1!

Cn is the number of Dyck words of length 2n. A For example, the following are the Dyck words of length 6:

XXXYYY XYXXYY XYXYXY XXYYXY XXYXYY.


class DyckWord
{
public static void printDyckWord(int xnum, int ynum, char[] str, int count)
{
if (xnum < 0 || ynum < xnum) return; // invalid state
if (xnum == 0 && ynum == 0)
{
System.out.println(str); // found one, so print it
}
else
{
if (xnum > 0) { // try a left paren, if there are some available
str[count] = 'X';
printDyckWord(xnum - 1, ynum, str, count + 1);
}
if (ynum > xnum) { // try a right paren, if there’s a matching left
str[count] = 'Y';
printDyckWord(xnum, ynum - 1, str, count + 1);
}
}
}

public static void printDyckWord(int count)
{
char[] str = new char[count*2];//As DyckWord is 2n length nX + nY
printDyckWord(count, count, str, 0);
}
public static void main(String a[])
{
printDyckWord(3);
}
}

Time Complexity O(n)
Space Complexity O(1)
Run Here http://www.ideone.com/pBgGO