Largest even number possible by using one swap operation in given number
Last Updated :
15 Sep, 2023
Given an odd number in the form of a string, the task is to make the largest even number from the given number, and you are allowed to do only one swap operation.
Examples :
Input: 1235785
Output: 1535782
Explanation: Swap 2 and 5.
Input: 536425
Output: 536524
Explanation: Swap 4 and 5 to make the largest even number.
- Find the first even number less than or equal to the odd number at the last index.
- If found, swap both values. Else swap with the last even value in the string.
- If not possible to make even, print the given string.
Implementation:
C++
#include <bits/stdc++.h>
using namespace std;
string makeEven(string& str)
{
int n = str.length();
int even = INT_MAX, index;
for ( int i = 0; i < n - 1; i++) {
if ((str[i] - '0' ) % 2 == 0) {
even = (str[i] - '0' );
index = i;
}
if (even <= (str[n - 1] - '0' ))
break ;
}
if (even == INT_MAX)
return str;
swap(str[index], str[n - 1]);
return str;
}
int main()
{
string str = "1356425" ;
cout << makeEven(str);
return 0;
}
|
Java
class GFG {
static char [] makeEven(String string)
{
char [] str = string.toCharArray();
int n = str.length;
int even = Integer.MAX_VALUE, index = 0 ;
for ( int i = 0 ; i < n - 1 ; i++) {
if ((str[i] - '0' ) % 2 == 0 ) {
even = (str[i] - '0' );
index = i;
}
if (even <= (str[n - 1 ] - '0' )) {
break ;
}
}
if (even == Integer.MAX_VALUE) {
return str;
}
swap(str, index, n - 1 );
return str;
}
static void swap( char [] str, int index1, int index2)
{
char temp = str[index1];
str[index1] = str[index2];
str[index2] = temp;
}
public static void main(String[] args)
{
String str = "1356425" ;
System.out.print(makeEven(str));
}
}
|
Python3
import sys
def makeEven(arr, n):
first_e_i = - 1
last_e_i = - 1
last_n_i = n - 1
for i in range (n):
if ( int (arr[i]) % 2 = = 0 and
int (arr[i]) < int (arr[last_n_i])):
first_e_i = i
break
if int (arr[i]) % 2 = = 0 :
last_e_i = i
if first_e_i ! = - 1 :
(arr[first_e_i],
arr[last_n_i]) = (arr[last_n_i],
arr[first_e_i])
return arr
if first_e_i = = - 1 and last_e_i ! = - 1 :
(arr[last_e_i],
arr[last_n_i]) = (arr[last_n_i],
arr[last_e_i])
return arr
return arr
if __name__ = = '__main__' :
string = "1356425"
result = "".join(makeEven( list (string),
len ( list (string))))
print (result)
|
C#
using System;
public class GFG {
static char [] makeEven(String str1)
{
char [] str = str1.ToCharArray();
int n = str.Length;
int even = int .MaxValue, index = 0;
for ( int i = 0; i < n - 1; i++) {
if ((str[i] - '0' ) % 2 == 0) {
even = (str[i] - '0' );
index = i;
}
if (even <= (str[n - 1] - '0' )) {
break ;
}
}
if (even == int .MaxValue) {
return str;
}
swap(str, index, n - 1);
return str;
}
static void swap( char [] str, int index1, int index2)
{
char temp = str[index1];
str[index1] = str[index2];
str[index2] = temp;
}
public static void Main()
{
String str = "1356425" ;
Console.WriteLine(makeEven(str));
}
}
|
PHP
<?php
function makeEven( $str )
{
$n = strlen ( $str );
$even = PHP_INT_MAX; $index ;
for ( $i = 0; $i < $n - 1; $i ++)
{
if (( $str [ $i ] - '0' ) % 2 == 0)
{
$even = ( $str [ $i ] - '0' );
$index = $i ;
}
if ( $even <= ( $str [ $n - 1] - '0' ))
break ;
}
if ( $even == PHP_INT_MAX)
return $str ;
list( $str [ $index ],
$str [ $n - 1]) = array ( $str [ $n - 1],
$str [ $index ]);
return $str ;
}
$str = "1356425" ;
echo makeEven( $str );
?>
|
Javascript
<script>
function makeEven(string) {
let str = string.split( '' );
let n = str.length;
let even = Number.MAX_VALUE, index = 0;
for (let i = 0; i < n - 1; i++) {
if ((str[i].charCodeAt() - '0' .charCodeAt()) % 2 == 0) {
even = (str[i] - '0' );
index = i;
}
if (even <= (str[n-1].charCodeAt() - '0' .charCodeAt())) {
break ;
}
}
if (even == Number.MAX_VALUE) {
return str;
}
swap(str,index, n - 1);
return str.join( "" );
}
function swap(str, index1, index2)
{
let temp = str[index1];
str[index1] = str[index2];
str[index2] =temp;
}
let str = "1356425" ;
document.write(makeEven(str));
</script>
|
Time Complexity: O(N)
Auxiliary Space: O(1)
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