C Program to accept an array & swap elements using pointers


November 27, 2021, Learn eTutorial
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This C program demonstrates how to accept an array of elements and swap the elements at desired positions using pointer. Before going into the program, we need to know more about pointers in C, and how this swapping of elements in an array can be executed using pointers.

What is a pointer?

A pointer is a variable that can able to store the address of another variable. Below are the steps to use a pointer in a program

  1. Define a pointer variable
  2. Assign the address of the variable to a Pointer
  3. Access the value at the address available in the Pointer variable

How to perform the swapping of array elements using pointers in C?

  • Initially declare the Array and define all the elements one by one.
  • Make a function with two pointer variables(let it be p1 and p2).
  • Inside this Function creates a temporary variable first, then this variable is assigned the value at the p1 pointer.
  • Now the value at the p1 pointer swaps the value to the p2 pointer.
  • Then, the value at the p2 pointer changes to the value of the temporary variable.

As a result, we get the array elements swapped at the desired position.

ALGORITHM

STEP 1: Include the header files to use the built-in functions in the C program.

STEP 2: Declare the Array x[20] as float and variables i, n, p1,p2 as integers.

STEP 3: Declare the function swap(float *ptr1, float *ptr2).

STEP 4: Read the number of elements into the variable n.

STEP 5: Read the elements of the Array into the array x+i using for loop.

STEP 6: Now call the Function swap(x+p1,x+p2) to interchange the p1 element by p2th.

STEP 7: Display the resultant Array as x[i] using for loop.

Function void swap(float *ptr1,float *ptr2)

STEP 1: Declare the variable temp as the float.

STEP 2: Assign temp=*ptr1.

STEP 3: *ptr1=*ptr2.

STEP 4: *ptr2=temp


To swap elements of an array using pointers in C programming, we have to learn the below concepts. We recommend you to learn those for better understanding

C Source Code

                                          #include <stdio.h>

void main() {
  float x[20];
  int i, n,p1,p2;
  void swap(float * ptr1, float * ptr2); /* Function Declaration */
  printf("How many Elements...\n");
  scanf("%d", & n);
  printf("Enter Elements one by one\n");
  for (i = 0; i < n; i++) {
    scanf("%f", x + i);
  }
  
  printf("Enter 2 Positions for swapping\n");
  scanf("%d %d", &p1;,&p2;);
  
  swap(x + p1, x + p2); /* Function call:Interchanging p1th element by p2th */
  printf("\nResultant Array...\n");
  for (i = 0; i < n; i++) {
    printf("X[%d] = %f\n", i, x[i]);
  }
} /* End of main() */

/* Function to swap any 2 elements in the array */

void swap(float * ptr1, float * ptr2) /* Function Definition */ {
  float temp;
  temp = * ptr1;
  * ptr1 = * ptr2;
  * ptr2 = temp;
}
                                      

OUTPUT

How many Elements...
10
Enter Elements one by one
10
20
30
40
50
60
70
80
90
100
Enter 2 Positions for swapping
3
7
Resultant Array...
X[0] = 10.000000
X[1] = 20.000000
X[2] = 30.000000
X[3] = 80.000000
X[4] = 50.000000
X[5] = 60.000000
X[6] = 70.000000
X[7] = 40.000000
X[8] = 90.000000
X[9] = 100.000000