Sudoku.c

@@ -0,0 +1,169 @@
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <time.h>
+
+char error[114] = "";
+void print(int a[9][9]) {
+	
+	int i,j;
+	for(i=0; i<=9; i++) {
+		if(i%3 == 0)
+			printf("|-----------------------|\n");
+		if(i >= 9) break;
+		printf("| ");
+		for(j=0; j<9; j++) {
+			if(a[i][j] > 0)
+				printf("%d ",a[i][j]);
+			else printf(". ");
+			if((j+1)%3 == 0)
+				printf("| ");
+		}
+		printf("\n");
+	}
+}
+
+void generate(int a[9][9]) {
+	memset(a, 0, sizeof(int) * 81);
+	
+	int i;
+	int x,y,z;
+	int t[10];
+	for(i = 0; i < 9; i++) {
+		if(i%3 == 0)
+			memset(t, 0, sizeof(t));
+		x = rand() % 9;
+		do {
+			y = rand() % 9;
+		}while(x == y);
+		do {
+			z = rand() % 9;
+		}while(x == z || y == z);
+		do {
+			a[i][x] = rand() % 9 + 1;
+		}while(t[a[i][x]]);
+		t[a[i][x]] = 1;
+		do {
+			a[i][y] = rand() % 9 + 1;
+		}while(t[a[i][y]]);
+		t[a[i][y]] = 1;
+		do {
+			a[i][z] = rand() % 9 + 1;
+		}while(t[a[i][z]]);
+		t[a[i][z]] = 1;
+	}
+	
+}
+
+int isSudoku(int a[9][9], const char* error) {
+	int t[10], i, j, x, y, sx, sy;
+	
+	for(i=0; i<9; i++) {
+		memset(t, 0, sizeof(t));
+		for(j=0; j<9; j++) {
+			if(t[a[i][j]]) {
+				sprintf(error, "The number %d in the row %d has been used!\n",
+					a[i][j], i+1);
+				return 0;
+			}
+			t[a[i][j]] = 1;
+			t[0] = 0;
+		}
+	}
+	
+	for(j=0; j<9; j++) {
+		memset(t, 0, sizeof(t));
+		for(i=0; i<9; i++) {
+			if(t[a[i][j]]) {
+				sprintf(error, "The number %d in the col %d has been used!\n",
+					a[i][j], j+1);
+				return 0;
+			}
+			t[a[i][j]] = 1;
+			t[0] = 0;
+		}
+	}
+	
+	for(x=0; x<2; x++)
+	for(y=0; y<2; y++) {
+		memset(t, 0, sizeof(t));
+		sx = x*3; sy = y*3;
+		for(i=sx; i<sx+3; i++)
+		for(j=sy; j<sy+3; j++) {
+			if(t[a[i][j]]) {
+				sprintf(error, "The number %d in the block %d has been used!\n",
+					a[i][j], x*3+y+1);
+				return 0;
+			}
+			t[a[i][j]] = 1;
+			t[0] = 0;
+		}
+	}
+	
+	return 1;
+}
+
+int _solve(int* it, int a[9][9]) {
+//	printf("%d\n", (void*)it - (void*)a);
+	int k; int* next = it;
+	
+	if(it >= (int*)a + 81) return 1;
+	
+	do {
+		next++;
+	}
+	while(*next > 0);
+			
+	for(k=1; k<=9; k++) {
+		*it = k;
+		if(isSudoku(a,error)) {
+//			print(a);
+			if(_solve(next, a)) // call stack
+				return 1;
+		}
+	}
+	// erase
+	*it = 0;
+	return 0;
+}
+
+int solve(int a[9][9]) {
+	int* it = a;
+	while(*it > 0)
+		it++;
+	return _solve(it, a);
+}
+
+int main() {
+	srand(time(0));
+	int a[9][9] = {{5, 3, 0, 0, 7, 0, 0, 0, 0}, 
+{6, 0, 0, 1, 9, 5, 0, 0, 0}, 
+{0, 9, 8, 0, 0, 0, 0, 6, 0}, 
+{8, 0, 0, 0, 6, 0, 0, 0, 3}, 
+{4, 0, 0, 8, 0, 3, 0, 0, 1}, 
+{7, 0, 0, 0, 2, 0, 0, 0, 6}, 
+{0, 6, 0, 0, 0, 0, 2, 8, 0}, 
+{0, 0, 0, 4, 1, 9, 0, 0, 5}, 
+{0, 0, 0, 0, 8, 0, 0, 7, 9}};
+//	generate(a);
+	
+	int valid = isSudoku(a, error);
+	
+	printf("The original Sudoku matrix:\n");
+	print(a);
+	
+	if(valid) {
+		printf("True:Valid initial Sudoku matrix!\n");
+	}
+	else {
+		printf("False:Invalid initial Sudoku matrix!\n      %s", error);
+	}
+	
+	if(valid && solve(a)) {
+		printf("The solution of Sudoku matrix:\n");
+		print(a);
+	}
+	else {
+		printf("No solution!");
+	}
+}