Question

How to swap the diagonals of a matrix in C

Answer 1

#include <stdio.h>

#define LEN 3

int main()
{
    int matrix[][LEN] = { { 1, 2, 3 }, 
	                      { 5, 6, 7 }, 
						  { 8, 7, 9 } };
	
	int rows = sizeof(matrix) / sizeof(matrix[0]);
    int cols = sizeof(matrix[0]) / sizeof(matrix[0][0]);

    for (int i = 0, j  = cols - 1; i < rows; i++, j--) {
        int tmp = matrix[i][i];
		matrix[i][i] = matrix[i][j];
		matrix[i][j] = tmp;
    }
		
	for (int i = 0; i < rows; i++) {
        for (int j = 0; j < cols; j++)
            printf("%3d", matrix[i][j]);
        printf("\n");
    }
	        
    return 0;
}
   
   
   
   
/*
run:
   
  3  2  1
  5  6  7
  9  7  8
  
*/

 

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