Largest even number possible by using one swap operation in given number in C++

In this tutorial, we are going to write a program that finds the largest possible even number with a single swap of digits.

Let's see the steps to solve the problem.

• Initialise the number in string format.
• Iterate over the given number.
  • Find the even digit that is less than or equal to the last digit of the number.
  • Break the loop if you find the desired even digit.
• If the even digit doesn't exist, then return the given number.
• Swap the last digit with the even digit you found in the above step.
• Return the number

Example

 Live Demo

#include <bits/stdc++.h>
using namespace std;
string getLargestEvenNumber(string number, int n) {
   int even = INT_MAX, index;
   for (int i = 0; i < n - 1; i++) {
      if ((number[i] - '0') % 2 == 0) {
         even = (number[i] - '0');
         index = i;
      }
      if (even <= (number[n - 1] - '0')) {
         break;
      }
   }
   if (even == INT_MAX) {
      return number;
   }
   swap(number[index], number[n - 1]);
   return number;
}
int main() {
   string number = "15433";
   cout << getLargestEvenNumber(number, 5) << endl;
   return 0;
}

Output

If you run the above code, then you will get the following result.

15334

Conclusion

If you have any queries in the tutorial, mention them in the comment section.

Hafeezul Kareem

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Updated on: 09-Apr-2021

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