# Nth Even length Palindrome

Given a number n as string, find the nth even-length positive palindrome number .

Examples:

```Input : n = "1"
Output : 11
1st even-length palindrome is 11 .

Input : n = "10"
Output : 1001
The first 10 even-length palindrome numbers are 11, 22,
33, 44, 55, 66, 77, 88, 99 and 1001.
```

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

As, it is a even-length palindrome so its first half should be equal to second half and length will be 2, 4, 6, 8 …. To evaluate nth palindrome let’s just see 1st 10 even-length palindrome numbers 11, 22, 33, 44, 55, 66, 77, 88, 99 and 1001 . Here, nth palindrome is nn’ where n’ is reverse of n . Thus we just have to write n and n’ in a consecutive manner where n’ is reverse of n .

Below is implementation of this approach .

## C/C++

```// C++ program to find n=th even length string.
#include <bits/stdc++.h>
using namespace std;

// Function to find nth even length Palindrome
string evenlength(string n)
{
// string r to store resultant
// palindrome. Initialize same as s
string res = n;

// In this loop string r stores
// reverse of string s after the
// string s in consecutive manner .
for (int j = n.length() - 1; j >= 0; --j)
res += n[j];

return res;
}

// Driver code to test above function
int main()
{
string n = "10";
cout << evenlength(n);
return 0;
}
```

## Java

```// Java program to find nth even length Palindrome
import java.io.*;

class GFG
{
// Function to find nth even length Palindrome
static String evenlength(String n)
{
// string r to store resultant
// palindrome. Initialize same as s
String res = n;

// In this loop string r stores
// reverse of string s after the
// string s in consecutive manner
for (int j = n.length() - 1; j >= 0; --j)
res += n.charAt(j);

return res;
}

// driver program
public static void main (String[] args)
{
String n = "10";
System.out.println(evenlength(n));
}
}

// Contributed by Pramod Kumar
```

Output:

``` 1001
```

Time Complexity : O(n)
This article is contributed by Surya Priy. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

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