#include <stdio.h>
#include <stdlib.h>

void permuteRec ( int m, int n, char *A, int i, int j )
{
   if ((i == m) && (j == n)) {
      printf("    %s\n", A);
      return;
   }
   if (i < m) { A[i+j] = 'R'; permuteRec(m,n,A,i+1,j); }
   if (j < n) { A[i+j] = 'G'; permuteRec(m,n,A,i,j+1); }
}

void permuteItr ( int m, int n )
{
   unsigned int i, j, t;
   int R, G;

   if (m + n > 31) {
      printf("!!! Sorry, the iterative method will not work...\n");
      return;
   }
   for (i=0; i<(1U<<(m+n)); ++i) {
      t = i; R = G = 0;
      for (j=0; j<m+n; ++j) {
         if (t & 1U) ++R; else ++G;
         t >>= 1;
      }
      if ((R == m) && (G == n)) {
         printf("    ");
         t = i;
         for (j=0; j<m+n; ++j) {
            printf("%c", (t & 1U) ? 'R' : 'G');
            t >>= 1;
         }
         printf("\n");
      }
   }
}

int main ()
{
   int m, n;
   char *A;

   do { printf("m = "); scanf("%d", &m); } while (m <= 0);
   do { printf("n = "); scanf("%d", &n); } while (n <= 0);

   printf("\n+++ Recursive method\n");
   A = (char *)malloc((m + n + 1) * sizeof(char));
   A[m+n] = '\0';
   permuteRec(m,n,A,0,0);

   printf("\n+++ Iterative method\n");
   permuteItr(m,n);

   exit(0);
}