Camden Dixie O'Brien
512580ab27
I expect this will probably generate some impossible puzzles, but I'll deal with that later.
126 lines
3.1 KiB
C
126 lines
3.1 KiB
C
/*
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* Copyright (C) 2022 Camden Dixie O'Brien
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Affero General Public License as
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* published by the Free Software Foundation, either version 3 of the
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* License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Affero General Public License for more details.
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*
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* You should have received a copy of the GNU Affero General Public
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* License along with this program. If not, see
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* <https://www.gnu.org/licenses/>.
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*/
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#include "sud.h"
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#include <assert.h>
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#include <stdio.h>
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#include <stdlib.h>
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#define FILLP_RCP 3
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static void initposs(struct sudoku *sud)
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{
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for (unsigned r = 0; r < SIDELEN; ++r) {
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for (unsigned c = 0; c < SIDELEN; ++c) {
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sud->cells[r][c].det = false;
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for (unsigned i = 0; i < NDIGITS; ++i)
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sud->cells[r][c].pvals[i] = true;
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}
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}
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}
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void gen(struct sudoku *sud)
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{
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initposs(sud);
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for (unsigned r = 0; r < SIDELEN; ++r) {
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for (unsigned c = 0; c < SIDELEN; ++c) {
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if (rand() % FILLP_RCP == 0) {
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assert(!sud->cells[r][c].det);
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unsigned val, n = 0;
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do {
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val = (unsigned)(rand() % NDIGITS);
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++n;
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} while (update(sud, r, c, val) == NOT_ALLOWED);
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}
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}
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}
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}
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enum update_res update(struct sudoku *sud, unsigned r, unsigned c, unsigned val)
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{
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unsigned tr, tc;
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assert(val < NDIGITS);
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/* Check that the cell is undetermined and the value is allowed. */
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if (sud->cells[r][c].det)
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return ALREADY_DET;
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if (!sud->cells[r][c].pvals[val])
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return NOT_ALLOWED;
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/* Update possible values of cells in same column. */
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for (tr = 0; tr < SIDELEN; ++tr) {
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if (tr == r || sud->cells[tr][c].det)
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continue;
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sud->cells[tr][c].pvals[val] = false;
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}
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/* Update possible values of cells in same row. */
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for (tc = 0; tc < SIDELEN; ++tc) {
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if (tc == c || sud->cells[r][tc].det)
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continue;
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sud->cells[r][tc].pvals[val] = false;
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}
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/* Update possible values of cells in same segment. */
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const unsigned segr0 = SEGLEN * (r / SEGLEN);
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const unsigned segc0 = SEGLEN * (c / SEGLEN);
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for (tr = segr0; tr < segr0 + SEGLEN; ++tr) {
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for (tc = segc0; tc < segc0 + SEGLEN; ++tc) {
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if ((tr == r && tc == c) || sud->cells[tr][tc].det)
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continue;
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sud->cells[tr][tc].pvals[val] = false;
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}
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}
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/* Set the cell's value. */
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sud->cells[r][c].det = true;
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sud->cells[r][c].val = val;
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return OK;
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}
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void print(const struct sudoku *sud)
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{
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for (unsigned r = 0; r < SIDELEN; ++r) {
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/*
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* Print horizontal divider if on a segment boundary (but not
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* at the start).
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*/
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if (r != 0 && r % SEGLEN == 0)
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puts("------+-------+------");
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for (unsigned c = 0; c < SIDELEN; ++c) {
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/*
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* Print vertical divider if on a segment boundary (but
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* not at the start).
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*/
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if (c != 0 && c % SEGLEN == 0)
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fputs("| ", stdout);
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if (sud->cells[r][c].det)
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printf("%u ", sud->cells[r][c].val + 1);
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else
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fputs(" ", stdout);
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}
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putchar('\n');
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}
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}
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