Sorciere.c

#include <stdio.h>
#include <string.h>

/* Tiles are labeled clockwise starting from the top.
   Colors are r(ed), y(ellow), g(reen), b(lue).
   Uppercase for head, lowercase for butt. */
char tiles[9][4] = {
	"yrGB",
	"RbyG",
	"BrbG",
	"RgyB",
	"YgrB",
	"brBY",
	"YryG",
	"RgyG",
	"rbBG" };

void print() {
	for (int r = 0; r < 3; ++r) {
		for (int c = 0; c < 3; ++c) printf(" %c ", tiles[3*r + c][0]);
		printf("\n");
		for (int c = 0; c < 3; ++c) printf("%c %c", tiles[3*r + c][3], tiles[3*r + c][1]);
		printf("\n");
		for (int c = 0; c < 3; ++c) printf(" %c ", tiles[3*r + c][2]);
		printf("\n");
	}
}
	
int match(char x, char y) {
	return (x^y) == ('A'^'a');
}

void rotate(int i) {
	char tmp = tiles[i][0];
	tiles[i][0] = tiles[i][1];
	tiles[i][1] = tiles[i][2];
	tiles[i][2] = tiles[i][3];
	tiles[i][3] = tmp;
}

void swap(int i, int j) {
	for (int n = 0; n < 4; ++n) {
		char tmp = tiles[i][n];
		tiles[i][n] = tiles[j][n];
		tiles[j][n] = tmp;
	}
}

void search(int i) {
	if (i == 9) {
		printf("Solution found:\n");
		print();
		return;
	}
	int r = i/3, c = i%3;
	for (int j = i; j < 9; ++j) {
		swap(i, j);
		for (int n = 0; n < 4; ++n) {
			if ((r == 0 || match(tiles[i][0], tiles[i - 3][2])) &&
			    (c == 0 || match(tiles[i][3], tiles[i - 1][1])))
				search(i + 1);
			rotate(i);
		}
		swap(i, j);
	}
}

int main() {
	search(0);
}

/* Output:

Solution found:
 G  G  B 
r Bb Bb G
 y  r  r 
 Y  R  R 
B bB gG g
 r  y  y 
 R  Y  Y 
G bB gG r
 y  r  y 
Solution found:
 G  B  r 
y Rr Yy G
 b  b  B 
 B  B  b 
r Yy Rr G
 g  g  B 
 G  G  b 
y Yy Rr B
 r  g  G 
Solution found:
 B  G  y 
r Yy Rr G
 g  g  Y 
 G  G  y 
r Bb Bb G
 y  r  R 
 Y  R  r 
B bB gG b
 r  y  B 
Solution found:
 B  r  r 
r Yy Gg B
 b  B  Y 
 B  b  y 
y Rr Gg G
 g  B  R 
 G  b  r 
B rR yY y
 b  G  G 
Solution found:
 y  r  y 
r Gg Bb G
 Y  Y  R 
 y  y  r 
g Gg Bb B
 R  R  Y 
 r  r  y 
G bB bB r
 B  G  G 
Solution found:
 G  G  b 
y Yy Rr B
 r  b  G 
 R  B  g 
G gG rR y
 y  b  B 
 Y  B  b 
B gG yY r
 r  r  B 
Solution found:
 B  y  r 
b Gg Bb B
 r  R  Y 
 R  r  y 
G bB bB r
 y  G  G 
 Y  g  g 
G rR yY r
 y  G  B 
Solution found:
 G  g  r 
B rR yY y
 b  G  G 
 B  g  g 
G rR yY r
 b  B  B 
 B  b  b 
G yY rR y
 r  B  G 
*/