How to concatenate two Integer values into one?

Given two integers n1 and n2, the task is to concatenate these two integers into one integer.
Example:

Input: n1 = 12, n2 = 34
Output: 1234

Input: n1 = 1, n2 = 93
Output: 193

Approach: The simplest approach to do this is: 

• Convert both numbers to string
• Concatenate both strings into one, as this is comparatively easy
• Convert this concatenated string back to integer

Program:

C++

// CPP program to concatenate
// two integers into one

#include <iostream>
#include <string>
using namespace std;

// Function to concatenate
// two integers into one
int concat(int a, int b)
{

    // Convert both the integers to string
    string s1 = to_string(a);
    string s2 = to_string(b);

    // Concatenate both strings
    string s = s1 + s2;

    // Convert the concatenated string
    // to integer
    int c = stoi(s);

    // return the formed integer
    return c;
}

int main()
{
    int a = 23;
    int b = 43;

    cout << concat(a, b) << endl;

    return 0;
}

// This code is contributed by Ayush Singla(@ayusin51)

C

// C program to concatenate
// two integers into one

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

// Function to concatenate
// two integers into one
int concat(int a, int b)
{

    char s1[20];
    char s2[20];

    // Convert both the integers to string
    sprintf(s1, "%d", a);
    sprintf(s2, "%d", b);

    // Concatenate both strings
    strcat(s1, s2);

    // Convert the concatenated string
    // to integer
    int c = atoi(s1);

    // return the formed integer
    return c;
}

int main()
{
    int a = 23;
    int b = 43;

    printf("%d\n", concat(a, b));

    return 0;
}

// This code is contributed by Ayush Singla(@ayusin51)

Java

// Java program to concatenate
// two integers into one

public class GFG {

    // Function to concatenate
    // two integers into one
    static int concat(int a, int b)
    {

        // Convert both the integers to string
        String s1 = Integer.toString(a);
        String s2 = Integer.toString(b);

        // Concatenate both strings
        String s = s1 + s2;

        // Convert the concatenated string
        // to integer
        int c = Integer.parseInt(s);

        // return the formed integer
        return c;
    }

    public static void main(String args[])
    {
        int a = 23;
        int b = 43;

        System.out.println(concat(a, b));
    }
}

Python3

# Python3 program to concatenate
# two integers into one

# Function to concatenate
# two integers into one
def concat(a, b):

    # Convert both the integers to string
    s1 = str(a)
    s2 = str(b)

    # Concatenate both strings
    s = s1 + s2

    # Convert the concatenated string
    # to integer
    c = int(s)

    # return the formed integer
    return c

# Driver code

a = 23
b = 43

print(concat(a, b))

# This code is contributed by shubhamsingh10

C#

// C# program to concatenate
// two integers into one
using System;

class GFG
{

    // Function to concatenate
    // two integers into one
    static int concat(int a, int b)
    {

        // Convert both the integers to string
        String s1 = a.ToString();
        String s2 = b.ToString();

        // Concatenate both strings
        String s = s1 + s2;

        // Convert the concatenated string
        // to integer
        int c = int.Parse(s);

        // return the formed integer
        return c;
    }

    // Driver code
    public static void Main(String []args)
    {
        int a = 23;
        int b = 43;

        Console.WriteLine(concat(a, b));
    }
}

/* This code contributed by PrinciRaj1992 */

Javascript

<script>

// JavaScript program to concatenate
// two integers into one


    // Function to concatenate
    // two integers into one
    function concat(a , b) {

        // Convert both the integers to string
        var s1 = a.toString();
        var s2 = b.toString();

        // Concatenate both strings
        var s = s1 + s2;

        // Convert the concatenated string
        // to integer
        var c = parseInt(s);

        // return the formed integer
        return c;
    }


        var a = 23;
        var b = 43;

        document.write(concat(a, b));

// This code contributed by Rajput-Ji

</script>

Output:

2343

Time Complexity: O(d1+d2) where d1=log₁₀(a) and d2=log₁₀(b)

Auxiliary Space: O(d1+d2)