gistfile1.c

#include <stdio.h>

void printDiagonals(int rows, int columns, int matrix[][columns])
{
	int iterations = rows + columns - 1;
	for(int i = 0; i < iterations; ++i) {
		int x = (i >= columns) ? columns-1 : i;
		int y = i-x;
		do {
			printf("%d ", matrix[y][x]);
			++y;
			x = i - y; // x+y = i
		} while(x >= 0 && y < rows);
		
		printf("\n");
	}
}

int main()
{
	int matrix[3][4] =
	{
		{3, 4, 5, 6},
		{6,22,56,2},
		{3,4, 9, 1},
	};
	
	printDiagonals(3, 4, matrix);
}

/* IT PRINTS

3 
4 6 
5 22 3 
6 56 4 
2 9 
1 

*/