C Program to Interchange Two Random Rows in a Matrix

In this article, we will write a C program to interchange two random rows in a matrix. Below are the inputs that will be taken from the user:

• The number of rows & columns in the matrix
• The elements in the matrix
• The rows that will be interchanged

Examples:

Input:

rows = 3, columns = 3

arr[i, j] = {{2, 1, 3}
                {1, 2, 6}
                {3, 8, 1}}

r1 = 2, r2 = 3

Output:

arr[i, j] = {{2, 1, 3}
                {3, 8, 1}
                {1, 2, 6}}

Input:

rows = 3, columns = 3

arr[i, j] = {{1, 2, 3}
                {4, 5, 6}
                {7, 8, 9}}

r1 = 1, r2 = 2

Output:

arr[i, j] = {{4, 5, 6}
                {1, 2, 3}
                {7, 8, 9}}

Approach: A simple & straightforward approach is to iterate through the matrix to reach the target rows and then swap the elements in both rows to get the desired matrix as output.

Example:

C

// C program to interchange two random rows in a matrix
#include <stdio.h>

int main()
{
    int rows, columns;

    printf("Enter the number of rows & columns: ");
    scanf("%d %d", &rows, &columns);

    int i, j, arr[10][10];

    printf("\nEnter the elements:\n\n");

    for (i = 0; i < rows; ++i) {
        for (j = 0; j < columns; ++j) {
            printf("Matrix[%d][%d]: ", i, j);
            scanf("%d", &arr[i][j]);
        }
    }

    printf("\nMatrix before interchanging rows:\n");

    for (i = 0; i < rows; ++i) {
        for (j = 0; j < columns; ++j) {
            printf("%d ", arr[i][j]);
        }

        printf("\n");
    }

    int r1, r2, temp;

    printf("\nEnter two row numbers that will be "
           "interchanged: ");
    scanf("%d %d", &r1, &r2);

    // Swap elements in both rows

    for (i = 0; i < rows; ++i) {
        temp = arr[r1 - 1][i];
        arr[r1 - 1][i] = arr[r2 - 1][i];
        arr[r2 - 1][i] = temp;
    }

    printf("\nMatrix after interchanging rows:\n");

    for (i = 0; i < rows; ++i) {
        for (j = 0; j < columns; ++j) {
            printf("%d ", arr[i][j]);
        }

        printf("\n");
    }

    return 0;
}

Output:

Enter the number of rows & columns: 3
3

Enter the elements:

Matrix[0][0]: 1
Matrix[0][1]: 2
Matrix[0][2]: 4
Matrix[1][0]: 5
Matrix[1][1]: 8
Matrix[1][2]: 9
Matrix[2][0]: 4
Matrix[2][1]: 2
Matrix[2][2]: 6

Matrix before interchanging rows:
1 2 4
5 8 9
4 2 6

Enter two row numbers that will be interchanged: 2
3

Matrix after interchanging rows:
1 2 4
4 2 6
5 8 9