# C Exercises: Swap two numbers using the function

## C Function : Exercise-3 with Solution

Write a program in C to swap two numbers using the function.

Test Data :
Input 1st number : 2
Input 2nd number : 4
Expected Output :

```Before swapping: n1 = 2, n2 = 4
After swapping: n1 = 4, n2 = 2 ```

C programming: swapping two variables

Swapping two variables refers to mutually exchanging the values of the variables. Generally, this is done with the data in memory.

The simplest method to swap two variables is to use a third temporary variable :

```define swap(a, b)
temp := a
a := b
b := temp
```

C Code:

```#include<stdio.h>

void swap(int *,int *);
int main()
{

int n1,n2;
printf("\n\n Function : swap two numbers using function :\n");
printf("------------------------------------------------\n");
printf("Input 1st number : ");
scanf("%d",&n1);
printf("Input 2nd number : ");
scanf("%d",&n2);

printf("Before swapping: n1 = %d, n2 = %d ",n1,n2);
//pass the address of both variables to the function.
swap(&n1,&n2);

printf("\nAfter swapping: n1 = %d, n2 = %d \n\n",n1,n2);
return 0;
}

void swap(int *p,int *q)
{
//p=&n1 so p store the address of n1, so *p store the value of n1
//q=&n2 so q store the address of n2, so *q store the value of n2

int tmp;
tmp = *p; // tmp store the value of n1
*p=*q;    // *p store the value of *q that is value of n2
*q=tmp;   // *q store the value of tmp that is the value of n1
}
```

C Practice online:

```#include<stdio.h>

void swap(int *,int *);
int main()
{

int n1,n2;
printf("\n\n Function : swap two numbers using function :\n");
printf("------------------------------------------------\n");
printf("Input 1st number : ");
scanf("%d",&n1);
printf("Input 2nd number : ");
scanf("%d",&n2);

printf("Before swapping: n1 = %d, n2 = %d ",n1,n2);
//pass the address of both variables to the function.
swap(&n1,&n2);

printf("\nAfter swapping: n1 = %d, n2 = %d \n\n",n1,n2);
return 0;
}

void swap(int *p,int *q)
{
//p=&n1 so p store the address of n1, so *p store the value of n1
//q=&n2 so q store the address of n2, so *q store the value of n2

int tmp;
tmp = *p; // tmp store the value of n1
*p=*q;    // *p store the value of *q that is value of n2
*q=tmp;   // *q store the value of tmp that is the value of n1
}
```

Improve this sample solution and post your code through Disqus.

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