Given a number n as a 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.
As, it is a even-length palindrome so its first half should be equal to reverse of 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 the implementation of this approach.
// 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 int main()
{ string n = "10" ;
// Function call
cout << evenlength(n);
return 0;
} |
// 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 code
public static void main(String[] args)
{
String n = "10" ;
// Function call
System.out.println(evenlength(n));
}
} // Contributed by Pramod Kumar |
# Python3 program to find n=th even # length string. import math as mt
# Function to find nth even length # Palindrome def evenlength(n):
# string r to store resultant
# palindrome. Initialize same as s
res = n
# In this loop string r stores
# reverse of string s after the
# string s in consecutive manner .
for j in range ( len (n) - 1 , - 1 , - 1 ):
res + = n[j]
return res
# Driver code n = "10"
# Function call print (evenlength(n))
# This code is contributed by # Mohit kumar 29 |
// C# program to find nth even // length Palindrome using System;
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[j];
return res;
}
// Driver code
public static void Main()
{
string n = "10" ;
// Function call
Console.WriteLine(evenlength(n));
}
} // This code is contributed by vt_m. |
<?php // PHP program to find n=th even length string. // Function to find nth even length Palindrome function evenlength( $n )
{ // string r to store resultant
// palindrome. Initialize same as s
$res = $n ;
// In this loop string r stores
// reverse of string s after the
// string s in consecutive manner .
for ( $j = strlen ( $n ) - 1; $j >= 0; -- $j )
$res = $res . $n [ $j ];
return $res ;
} // Driver code $n = "10" ;
// Function call echo evenlength( $n );
// This code is contributed by ita_c ?> |
<script> // Javascript program to find nth even length Palindrome // Function to find nth even length Palindrome
function evenlength(n)
{
// string r to store resultant
// palindrome. Initialize same as s
let res = n;
// In this loop string r stores
// reverse of string s after the
// string s in consecutive manner
for (let j = n.length - 1; j >= 0; --j)
res += n[j];
return res;
}
// Driver code
let n = "10" ;
// Function call
document.write(evenlength(n));
//This code is contributed by avanitrachhadiya2155
</script> |
1001
Time Complexity: O(n)
Auxiliary Space: O(n)