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C Program to Swap Two Numbers

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In this article, we will discuss how to write a C program to swap two number using a temporary variable and also without using a temporary or third variable.

For this purpose we are going to use Pointers, Functions, Arithmetic Operators, Bitwise Operators, Call By Reference in C concepts.

C Program to Swap Two Numbers

This C program allows the user to enter two integer values. Using the third variable, this program will Swap those two numbers.

/* C Program to Swap Two Numbers */

#include 

int main()
{
  int a, b, Temp;
 
  printf("\nPlease Enter the value of a and b\n");
  scanf("%d %d", &a, &b);
 
  printf("\nBefore Swap: a = %d and b = %d\n", a, b);
 
  Temp = a;
  a    = b;
  b    = Temp;
 
  printf("\nAfter Swapping: a = %d and b = %d\n", a, b);
 
  return 0;
}

OUTPUT

C Program to Swap Two Numbers

ANALYSIS
In the above example, we assigned a = 6 and b = 13

Temp = a – it means assigning the a value to the Temp variable
Temp = 6

a = b – it means assigning the b value to the variable a
a = 13

b = Temp – it means assigning the Temp value to the variable b
b = 6
Last Printf statement will print the a, b values as output.

C Program to Swap Two Numbers Using Pointers

This program allows the user to enter two integer values. By using the Pointers in C concept, this program will Swap two numbers. Within the main Function, we are using the third variable Temp to Swap those two numbers.

/* C Program to Swap Two Numbers Using Pointers */

#include <stdio.h>

int main()
{
  int a, b, *i, *j, Temp;
 
  printf("\nPlease Enter the value of a and b\n");
  scanf("%d %d", &a, &b);
 
  printf("\nBefore Swap: a = %d  b = %d\n", a, b);
  i = &a;
  j = &b;
  
  Temp = *i;
  *i    = *j;
  *j    = Temp;
 
  printf("\nAfter Swapping: a = %d  b = %d\n", a, b);
  printf("\nAfter Swapping: i = %d  j = %d\n", *i, *j);

  return 0;
}

OUTPUT

C Program to Swap Two Numbers Using Pointers

ANALYSIS
Below statements will assign the address of the variables a and b to the pointer variables i and j addresses

  i = &a;
  j = &b;

Below printf statement will display the values inside the variables a and b

printf("\nAfter Swapping: a = %d b = %d\n", a, b);

Below printf statement will display the values inside the pointer variables i and j

  printf("\nAfter Swapping: i = %d  j = %d\n", *i, *j);

C Program to Swap Two Numbers Using Functions

This program allows the user to enter two integer values. By using the Call By Value concept in Functions, this program will Swap two numbers.

Within the Function Swap, we are using the third variable Temp to Swap those two numbers.

/* C Program to Swap Two Numbers Using Functions */

#include <stdio.h>
 
void Swap(int, int);
 
int main()
{
  int A, B;
 
  printf("\nPlease Enter the value of A and B\n");
  scanf("%d %d", &A, &B);
 
  printf("\nBefore Swap: A = %d and A = %d\n", A, B);
 
  Swap(A, B); 
 
  return 0;
}
 
void Swap(int A, int B)
{
  int Temp;
 
  Temp = A;
  A = B;
  B = Temp;   
  
  printf("\nAfter Swapping: A = %d and B = %d\n", A, B);
}

OUTPUT

C Program to Swap Two Numbers Using Functions

ANALYSIS
When the compiler reaches the Swap(A, B); then, the compiler will automatically jump to the corresponding function

void Swap(int A, int B)

The working procedure of this function is the same as the above program. If you don’t understand the steps then please refer the C Program to Swap Two Number Analysis part.

C Program to Swap Two Numbers Using Call By Reference

This program allows the user to enter two integer values. By using the Functions Call By Reference concept (or Pointers concept), this program will Swap two number. Within the Function Swap, we are using the third variable Temp to Swap those two numbers.

Please Refer Call By Reference Example in PASSING PARAMETER TO THE FUNCTION article to see the functionality.

C Program to Swap Two Numbers Without Using Temp Variable

In this program, Instead of using the temp or third variable to swap two numbers We are going to use Arithmetic Operators in C.

/* C Program to Swap Two Numbers Without Using Temp Variable */
#include <stdio.h>

int main()
{
  int a, b;
 
  printf("\nPlease Enter the value of a and b\n");
  scanf("%d %d", &a, &b);
 
  printf("\nBefore Swap: a = %d  b = %d\n", a, b);
 
  a = a + b;
  b = a - b; 
  a = a - b;
 
  printf("\nAfter Swapping: a = %d  b = %d\n", a, b);
 
  return 0;
}

OUTPUT

C Program to Swap Two Numbers Without Using Temp Variable

ANALYSIS
User Entered Values are a =20 and b = 10

a = a + b;
a = 20 + 10 = 30

b = a – b;
b = 30 -10 = 20

a = a – b;
a = 30 – 20 = 10
Final Values after swapping 2 numbers: a = 10 and b = 20

NOTE: Although we can swap 2 numbers using multiplication and division approach. However, they may produce strange values if we are working with larger integer values or if any of the integer value is 0

C Program to Swap Two Numbers Using Bitwise OR Operator

In this program, Instead of using the temp or third variable to swap 2 numbers We are going to use Bitwise Operators in C.

/* C Program to Swap Two Numbers Using Bitwise OR Operator */
#include <stdio.h>

int main()
{
  int a, b;
 
  printf("\nPlease Enter the value of a and b\n");
  scanf("%d %d", &a, &b);
 
  printf("\nBefore Swap: a = %d  b = %d\n", a, b);
 
  a = a ^ b;
  b = a ^ b; 
  a = a ^ b;
 
  printf("\nAfter Swapping: a = %d  b = %d\n", a, b);
 
  return 0;
}

OUTPUT

C Program to Swap Two Numbers Using Bitwise OR Operator

ANALYSIS
User Entered Values are a = 8 and b = 4. The binary values of 8 = 1000 and 4 = 0010.

a = a ^ b
a = 1000 ^ 0010
a = 1010

b = a ^ b
b = 1010 ^ 0010
b = 1000

a = a ^ b;
a = 1010 ^ 1000
a = 0010
Final Values after swapping 2 numbers: a = 4 and b = 8

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