Print matrix diagonal and secondary Diagonal elements :

int mat[3][3]={
{1,2,3},
{4,5,6},
{7,8,9}
};
for(int i=0;i< 3;i++)
printf("%d",mat[i][i]);
printf("\n\n");
for(i=0;i< 3;i++)
printf("%d",mat[i][3-i-1]);

// somthing intreating of coding... lets C first.