C++ Program to Interchange Elements of First and Last Rows in Matrix

19/06/2024 0 By indiafreenotes

Interchanging elements of the first and last rows of a matrix involves swapping the elements of the first row with the corresponding elements of the last row.

Problem Statement

Given a matrix, interchange the elements of the first row with those of the last row.

Approach

  1. Initialization: Verify the matrix is valid (non-empty and has more than one row).
  2. Swapping Elements: Iterate through each column of the matrix and swap the elements of the first row with the corresponding elements of the last row.

Example

For a 3×3 matrix:

Matrix before interchange:

1 2 3

4 5 6

7 8 9

Matrix after interchange:

7 8 9

4 5 6

1 2 3

C++ Code Implementation

Here is a C++ program to interchange the elements of the first and last rows of a matrix:

#include <iostream>

#include <vector>

using namespace std;

// Function to interchange elements of the first and last rows of a matrix

void interchangeFirstLastRows(vector<vector<int>>& matrix) {

    int numRows = matrix.size();

    if (numRows < 2) {

        cout << “Matrix must have at least two rows to interchange.” << endl;

        return;

    }

    int numCols = matrix[0].size();

    for (int col = 0; col < numCols; ++col) {

        swap(matrix[0][col], matrix[numRows – 1][col]);

    }

}

// Function to print a matrix

void printMatrix(const vector<vector<int>>& matrix) {

    for (const auto& row : matrix) {

        for (const auto& elem : row) {

            cout << elem << ” “;

        }

        cout << endl;

    }

}

int main() {

    // Initializing a 3×3 matrix

    vector<vector<int>> matrix = {

        {1, 2, 3},

        {4, 5, 6},

        {7, 8, 9}

    };

    cout << “Matrix before interchange:” << endl;

    printMatrix(matrix);

    // Interchanging the first and last rows

    interchangeFirstLastRows(matrix);

    cout << “Matrix after interchange:” << endl;

    printMatrix(matrix);

    return 0;

}

Explanation

  1. Function interchangeFirstLastRows:

  • Parameters: Takes a 2D vector (matrix).
  • Validation: Checks if the matrix has at least two rows. If not, it outputs a message and returns.
  • Swapping Elements: Uses a loop to iterate through each column, swapping the elements of the first row with the corresponding elements of the last row.
  1. Function printMatrix:

  • Parameters: Takes a 2D vector (matrix).
  • Printing: Iterates through the matrix and prints its elements in a formatted manner for better visualization.
  1. Main Function:

  • Matrix Initialization: Creates a sample 3×3 matrix.
  • Printing Before Interchange: Prints the matrix before interchanging the rows.
  • Row Interchange: Calls the interchangeFirstLastRows function to swap the first and last rows.
  • Printing After Interchange: Prints the matrix after interchanging the rows.