Write a C program to swap the two values using pointers

Write a C program to swap the two values using pointers

Method 1.

In this program we are going to swap two numbers using pointers. The pointer will be used to hold the address of the variable and using pointer address of the variables will be swepped. In the following example we are going to implement this theory. 

  •  Program:

#include<stdio.h>
#include<conio.h>
    
void main()
{

//Declaration of variables and pointer variables
int x,y,*ptr_x,*ptr_y,temp;  

//Insert value of x and y
printf("Enter the value of x and y\n");
scanf("%d%d", &x, &y);

//Printing value before swapping
printf("Before Swapping\nx = %d\ny = %d\n", x, y);

//Assigning address of variables to pointers
ptr_x = &x;
ptr_y = &y;

//Swapping pointer address with the help of temp variable
temp = *ptr_y;
*ptr_y = *ptr_x;
*ptr_x = temp;

//printing values of x and y
printf("After Swapping\nx = %d\ny = %d\n", x, y);
getch();
}

  •  Output:

Enter the value of x and y
100 123
Before Swapping
x = 100
y = 123
After Swapping
x = 123
y = 100


Method 2.

Logic To Swap Two Numbers using Pointers and Function

We ask the user to enter values for variable a and b. We pass the address of variable a and b to function swap().

Inside function swap() we take a local variable temp. Since address of variable a and b are passed to swap() method, we take 2 pointer variables *x and *y. Pointer variable x holds the address of a and pointer variable y holds the address of b. Using below logic we swap the values present at address a( or x ) and b( or y ).

temp = *x;
*x = *y;
*y = temp;

Since we are directly changing the value present at particular address, the value gets reflected throughout the program and not just inside particular function. That’s why we are able to print the result inside main function and the values of variable a and b are swapped, without getting any returned value from function swap().

  •  Program:

#include<stdio.h>
#include<conio.h>
    
void swap(int*, int*);
int main()
{
    int a, b;

    printf("Enter the value for a and b\n");
    scanf("%d%d", &a, &b);

    printf("\n\nBefore swapping: a = %d and b = %d\n",a, b);
    swap(&a, &b);
    printf("\nAfter sawpping: a = %d and b = %d\n", a, b);
    return 0;
}
void swap(int *x, int *y)
{
    int temp;

    temp = *x;
    *x = *y;
    *y = temp;
}

  •  Output:

Enter the value for a and b
100
200


Before swapping: a = 100 and b = 200

After sawpping: a = 200 and b = 100

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