通过使用给定数量的一个交换操作可能的最大偶数

给定一个字符串形式的奇数，任务是从给定的数字中产生最大的偶数，并且您只能进行一次交换操作。
例子：

Input : 1235785
Output :1535782
Swap 2 and 5.

Input :  536425
Output :  536524
Swap 4 and 5 to make the largest even number.

在最后一个索引处找到小于或等于奇数的第一个偶数。
如果找到，交换两个值。否则与字符串中的最后一个偶数值交换。
如果不可能，打印给定的字符串。

C++

// C++ program for above implementation
#include 
using namespace std;
 
// Make the largest even number
string makeEven(string str)
{
    int n = str.length();
    int even = INT_MAX, index;
 
    // Start traversing the string
    for (int i = 0; i < n - 1; i++) {
 
        // Find the even number
        if ((str[i] - '0') % 2 == 0) {
            even = (str[i] - '0');
            index = i;
        }
 
        // Check if current even is equal to
        // or less than the odd number
        if (even <= (str[n - 1] - '0'))
            break;
    }
 
    // Return original string if there is no
    // even value
    if (even == INT_MAX)
        return str;
 
    // Swap even and odd value
    swap(str[index], str[n - 1]);
 
    return str;
}
 
// Driver code
int main()
{
    string str = "1356425";
    cout << makeEven(str);
    return 0;
}

Java

// Java program for above implementation
 
class GFG {
 
// Make the largest even number
    static char[] makeEven(String string) {
        char []str = string.toCharArray();
        int n = str.length;
        int even = Integer.MAX_VALUE, index = 0;
 
        // Start traversing the String
        for (int i = 0; i < n - 1; i++) {
 
            // Find the even number
            if ((str[i] - '0') % 2 == 0) {
                even = (str[i] - '0');
                index = i;
            }
 
            // Check if current even is equal to
            // or less than the odd number
            if (even <= (str[n-1] - '0')) {
                break;
            }
        }
 
        // Return original String if there is no
        // even value
        if (even == Integer.MAX_VALUE) {
            return str;
        }
 
        // Swap even and odd value
        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;
}
// Driver code
    public static void main(String[] args) {
        String str = "1356425";
        System.out.print(makeEven(str));
    }
}
/*This code is contributed by PrinciRaj1992*/

Python3

# Python3 code for the above implementation
import sys
 
# Make the largest even number
def makeEven(arr, n):
     
    # index to first even no,if any
    first_e_i = -1
     
    # index to last even no, if any
    last_e_i = -1
     
    # index to last no
    last_n_i = n - 1
 
    # Start traversing the String
    for i in range(n):
 
        # if it finds any first even no less
        # than last digit then break the loop
        if (int(arr[i]) % 2 == 0 and
            int(arr[i]) < int(arr[last_n_i])):
            first_e_i = i
            break
             
        # it finds last even no
        if int(arr[i]) % 2 == 0:
            last_e_i = i
    if first_e_i != -1:
         
        # swap even and odd value
        (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:
         
        # swap even and odd value
        (arr[last_e_i],
         arr[last_n_i]) = (arr[last_n_i],
                           arr[last_e_i])
        return arr
         
    # Return original String if there is
    # no even number
    return arr    
 
# Driver Code
if __name__=='__main__':
    string="1356425"
    result = "".join(makeEven(list(string),
                          len(list(string))))
    print(result)
  
# This code is contributed
# by Vikash Kumar 37

C#

// C# implementation of above approach
using System;
 
public class GFG {
  
// Make the largest even number
    static char[] makeEven(String str1) {
        char []str = str1.ToCharArray();
        int n = str.Length;
        int even = int.MaxValue, index = 0;
  
        // Start traversing the String
        for (int i = 0; i < n - 1; i++) {
  
            // Find the even number
            if ((str[i] - '0') % 2 == 0) {
                even = (str[i] - '0');
                index = i;
            }
  
            // Check if current even is equal to
            // or less than the odd number
            if (even <= (str[n-1] - '0')) {
                break;
            }
        }
  
        // Return original String if there is no
        // even value
        if (even == int.MaxValue) {
            return str;
        }
  
        // Swap even and odd value
        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;
}
// Driver code
    public static void Main() {
        String str = "1356425";
        Console.WriteLine(makeEven(str));
    }
}
/*This code is contributed by PrinciRaj1992*/

PHP

Javascript

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