Write a C program to read elements in a matrix and interchange elements of primary(major) diagonal with secondary(minor) diagonal. C program for interchanging diagonals of a matrix.

1 2 3

4 5 6

7 8 9

Matrix after interchanging its diagonal:

3 2 1

4 5 6

9 8 7

Logic to interchange diagonals of matrix

Step 1: temp = A[row][col]

Step 2: A[row][col] = A[row][ (N-col)-1 ] (Where N is the size of array).

Step 3: A[row][ (N-col)-1 ] = temp.

Happy coding ;)

**Example:**If elements of matrix are:1 2 3

4 5 6

7 8 9

Matrix after interchanging its diagonal:

3 2 1

4 5 6

9 8 7

### Required knowledge:

Basic C programming, For loop, Array, Matrix### Algorithm:

Logic to interchange diagonals of matrix

**A**:Step 1: temp = A[row][col]

Step 2: A[row][col] = A[row][ (N-col)-1 ] (Where N is the size of array).

Step 3: A[row][ (N-col)-1 ] = temp.

### Program:

/** * C program to interchange diagonals of a matrix */ #include <stdio.h> #define MAX_ROWS 3 #define MAX_COLS 5 int main() { int A[MAX_ROWS][MAX_COLS]; int row, col, square, temp; /* * Reads elements in matrix from user */ printf("Enter elements in matrix of size %dx%d: \n", MAX_ROWS, MAX_COLS); for(row=0; row < MAX_ROWS; row++) { for(col=0; col < MAX_COLS; col++) { scanf("%d", &A[row][col]); } } square = (MAX_ROWS < MAX_COLS) ? MAX_ROWS : MAX_COLS; /* * Interchanges diagonal of the matrix */ for(row=0; row < square; row++) { col = row; temp = A[row][col]; A[row][col] = A[row][(square - col)-1]; A[row][(square - col)-1] = temp; } /* * Prints the interchanged diagonals matrix */ printf("\nMatrix after diagonals interchanged: \n"); for(row=0; row < MAX_ROWS; row++) { for(col=0; col < MAX_COLS; col++) { printf("%d ", A[row][col]); } printf("\n"); } return 0; }

Output

Enter elements in matrix of size 3x3:

1 2 3

4 5 6

7 8 9

Matrix after diagonals interchanged:

3 2 1

4 5 6

9 8 7

1 2 3

4 5 6

7 8 9

Matrix after diagonals interchanged:

3 2 1

4 5 6

9 8 7

Happy coding ;)

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