Java Program to Interchange Elements of First and Last in a Matrix Across Rows - GeeksforGeeks

30 Mar, 2021
For a given 4 × 4 matrix, the task is to interchange the elements of the first and last rows and then return the resultant matrix.
Illustration:
Input 1:  1  1  5  0
          2  3  7  2
          8  9  1  3
          6  7  8  2
Output 1: 6  7  8  2
          2  3  7  2 
          8  9  1  3
          1  1  5  0

Input 2:  7   8   9  10
         11  13  14   1
         15   7  12  22
         11  21  30   1

Output 2: 11  21  30   1
         11  13  14   1
         15  7   12  22
         7   8   9   10
Approach:
To get the required output, we need to swap the elements of the first and the last row of the stated matrix.
Example
Java
// Java Program to Interchange Elements of First// and Last Row in a Matrix  // Importing input output classesimport java.io.*;  // Main Classpublic class GFG {      // Method 1    // To swap First and Last Row    static void swap_First_last(int mat[][])    {        int rws = mat.length;          // Interchanging of elements between the        // first and last rows        for (int j = 0; j < mat[0].length; j++) {              // Using temporary variable so in order            // not to loose the values of the matrix            // Simply, swapping the values stored            int temp = mat[0][j];            mat[0][j] = mat[rws - 1][j];            mat[rws - 1][j] = temp;        }    }      // Method 2    // Main driver method    public static void main(String args[])        throws IOException    {        // Input integer matrix        int mat[][] = { { 2, 3, 4, 5 },                        { 8, 9, 6, 15 },                        { 13, 22, 11, 18 },                        { 19, 1, 2, 0 } };          // Display message only        System.out.println("Input matrix is as follows : ");          // Printing the Input matrix        for (int j = 0; j < mat.length; j++) {            for (int k = 0; k < mat[0].length; k++)                  // Print the elements of the input matrix                System.out.print(mat[j][k] + " ");              // New line as row ended            System.out.println();        }          System.out.println(            "Swapped matrix is as follows : ");          // Calling the (method1) to swap rows in a matrix        swap_First_last(mat);          // Printing the Swapped matrix        for (int j = 0; j < mat.length; j++) {            for (int k = 0; k < mat[0].length; k++)                  // Print the elements of the swapped matrix                System.out.print(mat[j][k] + " ");              // New line as row ended            System.out.println();        }    }}
Input matrix is as follows : 
2 3 4 5 
8 9 6 15 
13 22 11 18 
19 1 2 0 
Swapped matrix is as follows : 
19 1 2 0 
8 9 6 15 
13 22 11 18 
2 3 4 5

arorakashish0911
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