ref: 2810cc5d0c01b06e678b50995edb724c739b8eed
dir: /sys/src/games/sudoku/game.c/
#include <u.h>
#include <libc.h>
#include <draw.h>
#include "sudoku.h"
int allowbits[Brdsize] = {
0x00100,
0x00200,
0x00400,
0x00800,
0x01000,
0x02000,
0x04000,
0x08000,
0x10000
};
int boxind[Brdsize][Brdsize] = {
{0,1,2,9,10,11,18,19,20},
{3,4,5,12,13,14,21,22,23},
{6,7,8,15,16,17,24,25,26},
{27,28,29,36,37,38,45,46,47},
{30,31,32,39,40,41,48,49,50},
{33,34,35,42,43,44,51,52,53},
{54,55,56,63,64,65,72,73,74},
{57,58,59,66,67,68,75,76,77},
{60,61,62,69,70,71,78,79,80},
};
int colind[Brdsize][Brdsize] = {
{0,9,18,27,36,45,54,63,72},
{1,10,19,28,37,46,55,64,73},
{2,11,20,29,38,47,56,65,74},
{3,12,21,30,39,48,57,66,75},
{4,13,22,31,40,49,58,67,76},
{5,14,23,32,41,50,59,68,77},
{6,15,24,33,42,51,60,69,78},
{7,16,25,34,43,52,61,70,79},
{8,17,26,35,44,53,62,71,80},
};
int rowind[Brdsize][Brdsize] = {
{0,1,2,3,4,5,6,7,8},
{9,10,11,12,13,14,15,16,17},
{18,19,20,21,22,23,24,25,26},
{27,28,29,30,31,32,33,34,35},
{36,37,38,39,40,41,42,43,44},
{45,46,47,48,49,50,51,52,53},
{54,55,56,57,58,59,60,61,62},
{63,64,65,66,67,68,69,70,71},
{72,73,74,75,76,77,78,79,80},
};
static int maxlevel;
static int solved;
void
printbrd(int *board)
{
int i;
for(i = 0; i < Psize; i++) {
if(i > 0 && i % Brdsize == 0)
print("\n");
print("%2.2d ", board[i] & Digit);
}
print("\n");
}
int
getrow(int cell)
{
return cell/9;
}
int
getcol(int cell)
{
return cell%9;
}
int
getbox(int cell)
{
int row = getrow(cell);
int col = getcol(cell);
return 3*(row/3)+ col/3;
}
void
setdigit(int cc, int num)
{
board[cc] = (board[cc] & ~Digit) | num;
}
int
boxcheck(int *board)
{
int i,j,d,sum,last,last2;
for (i = 0; i < 9; i++) {
for (d = 0;d < 9; d++) {
sum=0;
last=-1;
last2=-1;
for (j = 0; j < 9; j++) {
if (board[boxind[i][j]] & allowbits[d]) {
sum++;
last2=last;
last=boxind[i][j];
} else
sum += ((board[boxind[i][j]] & Solve)==(d << 4)) ? 1: 0;
}
if (sum==0)
return(0);
if ((sum==1)&&(last>=0))
if (!setallowed(board,last,d))
return(0);
if((sum == 2) && (last >= 0) && ( last2 >= 0) &&
(getrow(last) == getrow(last2))) {
for (j = 0; j < 9; j++) {
int c = rowind[getrow(last)][j];
if ((c != last)&&(c != last2)) {
if (board[c] & allowbits[d]) {
board[c] &= ~allowbits[d];
if ((board[c] & Allow)==0)
return(0);
}
}
}
}
if((sum == 2) && (last >= 0) && (last2 >= 0) &&
(getcol(last) == getcol(last2))) {
for (j = 0;j <9;j++) {
int c = colind[getcol(last)][j];
if ((c != last) && (c != last2)) {
if (board[c] & allowbits[d]) {
board[c] &= ~allowbits[d];
if ((board[c] & Allow) == 0)
return(0);
}
}
}
}
}
}
return(1);
}
int
rowcheck(int *board)
{
int i,j,d,sum,last;
for (i = 0; i < 9; i++) {
for (d = 0; d < 9; d++) {
sum = 0;
last = -1;
for (j = 0; j <9 ; j++) {
if (board[rowind[i][j]] & allowbits[d]) {
sum++;
last = j;
} else
sum += ((board[rowind[i][j]] & Solve) == (d << 4)) ? 1: 0;
}
if (sum == 0)
return(0);
if ((sum == 1) && (last >= 0)) {
if (!setallowed(board, rowind[i][last], d))
return(0);
}
}
}
return(1);
}
int
colcheck(int *board)
{
int i,j,d,sum,last;
for (i = 0; i < 9; i++) {
for (d = 0; d < 9; d++) {
sum = 0;
last = -1;
for (j = 0;j < 9;j++) {
if (board[colind[i][j]] & allowbits[d]) {
sum++;
last = j;
} else
sum += ((board[colind[i][j]] & Solve) == (d << 4)) ? 1: 0;
}
if (sum == 0)
return(0);
if ((sum == 1) && (last >= 0)) {
if (!setallowed(board, colind[i][last], d))
return(0);
}
}
}
return(1);
}
int
setallowed(int *board, int cc, int num)
{
int j, d;
int row, col, box;
board[cc] &= ~Allow;
board[cc] = (board[cc] & ~Solve) | (num << 4);
row = getrow(cc);
for (j = 0; j < 9; j++) {
if (board[rowind[row][j]] & allowbits[num]) {
board[rowind[row][j]] &= ~allowbits[num];
if ((board[rowind[row][j]] & Allow) == 0)
return(0);
}
}
col = getcol(cc);
for (j = 0; j < 9; j++) {
if (board[colind[col][j]] & allowbits[num]) {
board[colind[col][j]] &= ~allowbits[num];
if ((board[colind[col][j]] & Allow) == 0)
return(0);
}
}
box = getbox(cc);
for (j = 0;j < 9;j++) {
if (board[boxind[box][j]] & allowbits[num]) {
board[boxind[box][j]] &= ~allowbits[num];
if ((board[boxind[box][j]] & Allow)==0)
return(0);
}
}
for (j = 0;j < 81; j++)
for (d = 0; d < 9; d++)
if ((board[j] & Allow) == allowbits[d])
if (!setallowed(board, j, d))
return(0);
if (!boxcheck(board)||!rowcheck(board)||!colcheck(board))
return(0);
for (j = 0; j < 81; j++)
for (d = 0; d < 9; d++)
if ((board[j] & Allow) == allowbits[d])
if (!setallowed(board, j, d))
return(0);
return(1);
}
int
chksolved(int *board)
{
int i;
for (i = 0; i < Psize; i++)
if ((board[i] & Allow) != 0)
return 0;
solved = 1;
return solved;
}
int
findmove(int *board)
{
int i, d;
int s;
s = nrand(Psize);
for (i=(s+1)%81;i!=s;i=(i+1)%81) {
if (!(board[i] & Allow)) {
d=(board[i] & Solve) >> 4;
if ((board[i] & Digit)!=d)
return(i);
}
}
return(-1);
}
void
attempt(int *pboard, int level)
{
int tb[Psize];
int i, j, k;
int s, e;
if (level > maxlevel)
maxlevel = level;
if (level > 25)
exits("level"); /* too much */
s = nrand(Psize);
for (i = (s + 1) % Psize; i != s; i = (i + 1) % Psize) {
if ((pboard[i] & Allow) != 0) {
e=nrand(9);
for (j = (e + 1) % 9; j != e; j = (j + 1) % 9) {
if (pboard[i] & allowbits[j]) {
for (k = 0; k < Psize; k++)
tb[k] = pboard[k];
if (setallowed(tb, i, j)) {
tb[i] = (tb[i] & ~Digit) | j;
if (chksolved(tb)) {
for (k = 0;k < Psize; k++)
pboard[k] = tb[k];
return; /* bad! */
}
attempt(tb, level + 1);
if (chksolved(tb)) {
for (k = 0; k < Psize; k++)
pboard[k] = tb[k];
return;
}
tb[i] |= Digit;
if (level > 25)
return;
}
}
}
}
}
}
void
solve(void)
{
int pboard[Psize];
int i, c;
if (!solved) {
for (i = 0; i < Psize; i++)
pboard[i] = Allow | Solve | Digit;
for (i = 0; i < Psize; i++) {
c = board[i] & Digit;
if ((0 <= c) && (c < 9)) {
if (!setallowed(pboard,i,c)) {
print("starting position impossible... failed at cell %d char: %d\n", i, c + 1);
return;
}
}
}
attempt(pboard,0);
for (i = 0; i < Psize; i++)
board[i] = (board[i] & ~Solve) | (pboard[i] & Solve);
}
}
int
checklegal(int cc, int d)
{
int hold = board[cc];
int j, row, col, box;
board[cc] |= Digit;
row = getrow(cc);
for (j = 0; j < Brdsize; j++)
if ((board[rowind[row][j]] & Digit) == d) {
board[cc] = hold;
return(0);
}
col = getcol(cc);
for (j = 0; j < Brdsize; j++)
if ((board[colind[col][j]] & Digit) == d) {
board[cc] = hold;
return(0);
}
box = getbox(cc);
for (j = 0; j < Brdsize; j++)
if ((board[boxind[box][j]] & Digit) == d) {
board[cc] = hold;
return(0);
}
board[cc]=hold;
return(1);
}
void
clearp(void)
{
int i;
for(i = 0; i < Psize; i++) {
board[i] = (Allow | Solve | Digit);
}
solved = 0;
}
void
makep(void)
{
int i,d;
do {
clearp();
maxlevel=0;
for (d = 0; d < Brdsize; d++) {
i = nrand(Psize);
if (board[i] & allowbits[d]) {
setallowed(board, i, d);
board[i] = (board[i] & ~Digit) | d;
}
}
attempt(board, 0);
for (i = 0; i < Psize; i++) {
if ((0 <= (board[i] & Digit)) && ((board[i] & Digit) < 9))
board[i] |= MLock;
setdigit(i, board[i] & Digit);
}
if (!solved) {
fprint(2, "failed to make puzzle\n");
exits("failed to make puzzle");
}
} while (!solved);
}