# C Program to Interchange Elements of First and Last in a Matrix Across Rows

• Last Updated : 19 Jul, 2022

Here, we will see how to interchange the elements of first and last in a matrix across rows. Below are the examples:

Input: 6 3 1
4 5 2
2 4 9
Output: 2 4 9
4 5 2
6 3 1

Input: 1 3 5
4 5 2
2 2 4
Output: 2 2 4
4 5 2
1 3 5

Approach: The approach is very simple, swap the elements of the first and last row of the matrix in order to get the desired matrix as output.

Below is the C program to interchange the elements of first and last in a matrix across rows:

## C

 `// C program interchange the elements``// of first and last in a matrix``// across rows.``#include ` `#define n 3` `// Function to swap the element``// of first and last row``void` `interchangeFirstLast(``int` `m[][n])``{``    ``int` `rows = n;` `    ``// Swapping of element between first``    ``// and last rows``    ``for` `(``int` `i = 0; i < n; i++)``    ``{``        ``int` `t = m[i];``        ``m[i] = m[rows - 1][i];``        ``m[rows - 1][i] = t;``    ``}``}` `// Driver code``int` `main()``{``    ``// Input matrix``    ``int` `m[n][n] = {{6, 3, 1},``                   ``{4, 5, 2},``                   ``{2, 4, 9}};` `    ``// Printing the input matrix``    ``printf``(``"Input Matrix: \n"``);``    ``for` `(``int` `i = 0; i < n; i++)``    ``{``        ``for` `(``int` `j = 0; j < n; j++)``        ``{``            ``printf``(``"%d "``, m[i][j]);``        ``}``        ``printf``(``"\n"``);``    ``}` `    ``// call interchangeFirstLast(m) function.``    ``// This function swap the element of``    ``// first and last row``    ``interchangeFirstLast(m);` `    ``// Printing the original matrix``    ``printf``(``"\nOutput Matrix: \n"``);``    ``for` `(``int` `i = 0; i < n; i++)``    ``{``        ``for` `(``int` `j = 0; j < n; j++)``        ``{``            ``printf``(``"%d "``, m[i][j]);``        ``}``        ``printf``(``"\n"``);``    ``}``}`

Output

```Input Matrix:
6 3 1
4 5 2
2 4 9

Output Matrix:
2 4 9
4 5 2
6 3 1 ```

Time Complexity: O(n2)
Auxiliary Space: O(1)

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