C Program to Swap two Numbers
Last Updated :
22 Mar, 2024
Swapping two numbers means exchanging their values. In this article, we will learn how to swap two numbers in the C programming language.
Swap Two Numbers Using a Temporary Variable
Below is the C program to swap two numbers using a temporary variable.
C
// C program to swap two variables
#include <stdio.h>
// Driver code
int main()
{
int x, y;
printf("Enter Value of x ");
scanf("%d", &x);
printf("\nEnter Value of y ");
scanf("%d", &y);
// Using a temporary variable to swap the values
// Store the value of x in a temporary variable
int temp = x;
// Assign the value of y to x
x = y;
// Assign the value stored in the temporary variable to
// y
y = temp;
printf("\nAfter Swapping: x = %d, y = %d", x, y);
return 0;
}
OutputEnter Value of x
Enter Value of y
After Swapping: x = 0, y = 0
Explanation
We swap two numbers by storing the value of one number in a temporary variable, assigning the value of the second number to the first number, and then assigning the value stored in the temporary variable to the second number.
Swap Two Numbers Without Using a Temporary Variable
Below is the C/C++ program to swap two numbers without using a temporary variable.
C
// C program to swap two numbers
// without using a third variable
#include <stdio.h>
// Driver code
int main()
{
int a, b;
printf("Enter the two numbers : \n");
scanf("%d %d", &a, &b);
printf("Before swapping A is : %d and B is %d \n", a,
b);
// Swapping without using a third variable
// Sum of both numbers is stored in 'a'
a = a + b;
// Difference of sum and original 'b' is
// stored in 'b'
b = a - b;
// Difference of sum and new 'b' is stored in
// 'a'
a = a - b;
printf("After swapping A is : %d and B is : %d \n", a,
b);
return 0;
}
OutputEnter the two numbers :
Before swapping A is : 0 and B is 32767
After swapping A is : 32767 and B is : 0
Complexity Analysis
Explanation
The idea is to use arithmetic operators. We will take the sum of the two numbers and store it in one number and store the difference of both numbers in the other number. Finally, we will store the difference of both numbers in the first number. Since the values will be updated after the first two operations we will be able to swap the numbers.
We can write a function also to swap twp variables if we need to repeatedly use swap
The idea is to use pointers in C. We use pointers because variables are passed by value in C and to change value of a variable inside another function, we need to pass address of the variable so that the value can changed by going to the address.
C
// C program for QuickSort
#include <stdio.h>
// function to swap tp integers
void swap(int *p1, int *p2) {
int temp = *p1;
*p1 = *p2;
*p2 = temp;
}
// Driver code
int main()
{
int x, y;
printf("Enter Value of x ");
scanf("%d", &x);
printf("\nEnter Value of y ");
scanf("%d", &y);
// Note that we are passing addresses
// of two variables
swap(&x, &y);
printf("\nAfter Swapping: x = %d, y = %d", x, y);
return 0;
}
Refer to the complete article on How to swap without using a temporary variable? for more details!
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