ab_x_cd_equal_to_ba_x_dc_v1.c

/*

    ab_x_cd_equal_to_ba_x_dc_v1.c


    Find the two-digit numbers that apply to:

    ab * cd = ba = dc


    You can find all my C programs at Dragan Milicev's pastebin:

    https://pastebin.com/u/dmilicev

*/

#include <stdio.h>

int main(void)
{
    int a,b,c,d, counter=0;

    for(a=0; a<=9; a++)
      for(b=0; b<=9; b++)
        for(c=0; c<=9; c++)
          for(d=0; d<=9; d++)
          {
            if( (a*10+b)*(c*10+d) == (b*10+a)*(d*10+c) &&
                (a*10+b) > 9 &&
                (b*10+a) > 9 &&
                (c*10+d) > 9 &&
                (d*10+c) > 9    )
            {
                printf("\n %2d * %2d = %2d * %2d = %4d \n",
                  a*10+b, c*10+d, b*10+a, d*10+c, (a*10+b)*(c*10+d) );
                counter++;
            }
          }

          printf("\n There are %d pairs of such numbers. \n", counter );

    return 0;

} // main()