In C, to swap two rows of a matrix mat of size n x n, which of the following statements is correct?

To swap two rows of a matrix in C, you will typically need to use either a temporary array or directly swap the elements of each row. Here’s how you can approach it:

1. Break Down the Problem

   • Identify the rows to be swapped (let's say row $i$ and row $j$).
   • Ensure you have access to all elements in those rows.

2. Relevant Concepts

   • Using a temporary array to hold one row’s data while you swap them.
   • Alternatively, using a loop to swap elements directly.

3. Analysis and Detail

   • Using a Temporary Array:

     void swapRows(int mat[n][n], int row1, int row2) {
         int temp[n];
         for (int k = 0; k < n; k++) {
             temp[k] = mat[row1][k]; // Copy row1 into temp
             mat[row1][k] = mat[row2][k]; // Copy row2 into row1
             mat[row2][k] = temp[k]; // Copy temp into row2
         }
     }
     

   • Directly Swapping Elements:

     void swapRows(int mat[n][n], int row1, int row2) {
         for (int k = 0; k < n; k++) {
             int temp = mat[row1][k]; // Store element from row1
             mat[row1][k] = mat[row2][k]; // Assign from row2 to row1
             mat[row2][k] = temp; // Assign from temp to row2
         }
     }
     

4. Verify and Summarize

   • Both methods will successfully swap the specified rows.
   • The choice between them depends on whether you wish to use extra space (temporary array) or not.

Final Answer

The correct statement to swap two rows of a matrix mat of size n x n in C is to either use a temporary array to hold one of the rows during the swap or to swap elements directly in a loop without using extra space. Both approaches are valid depending on the requirements.