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Make generator always produce possible puzzles

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This commit is contained in:
Camden Dixie O'Brien 2022-11-21 19:22:53 +00:00
parent 5ae7a18227
commit d6b9f3e2e5
2 changed files with 67 additions and 20 deletions
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84
sud.c
View File

@ -22,12 +22,15 @@
#include <stdio.h>
#include <stdlib.h>
#define FILLP_RCP 3
#define REM_PROB_NUMER 2
#define REM_PROB_DENOM 3
#define MAX_FILL_ATTEMPTS 32
static void initposs(struct sudoku *sud)
{
for (unsigned r = 0; r < SIDELEN; ++r) {
for (unsigned c = 0; c < SIDELEN; ++c) {
for (unsigned r = 0; r < NDIGITS; ++r) {
for (unsigned c = 0; c < NDIGITS; ++c) {
sud->cells[r][c].det = false;
for (unsigned i = 0; i < NDIGITS; ++i)
sud->cells[r][c].pvals[i] = true;
@ -35,21 +38,66 @@ static void initposs(struct sudoku *sud)
}
}
static void clear(struct sudoku *sud, unsigned r, unsigned c)
{
unsigned tr, tc, val;
/* Set undetermined with all possible values */
sud->cells[r][c].det = false;
for (unsigned i = 0; i < NDIGITS; ++i)
sud->cells[r][c].pvals[i] = true;
/* Update cell's possible values based off column. */
for (tr = 0; tr < NDIGITS; ++tr) {
if (tr == r || !sud->cells[tr][c].det)
continue;
val = sud->cells[tr][c].val;
sud->cells[r][c].pvals[val] = false;
}
/* Update possible values of cells in same row. */
for (tc = 0; tc < NDIGITS; ++tc) {
if (tc == c || !sud->cells[r][tc].det)
continue;
val = sud->cells[r][tc].val;
sud->cells[r][c].pvals[val] = false;
}
/* Update possible values of cells in same segment. */
const unsigned segr0 = SEGLEN * (r / SEGLEN);
const unsigned segc0 = SEGLEN * (c / SEGLEN);
for (tr = segr0; tr < segr0 + SEGLEN; ++tr) {
for (tc = segc0; tc < segc0 + SEGLEN; ++tc) {
if ((tr == r && tc == c) || !sud->cells[tr][tc].det)
continue;
val = sud->cells[tr][tc].val;
sud->cells[r][c].pvals[val] = false;
}
}
}
void gen(struct sudoku *sud)
{
/* Generate a completed sudoku. */
retry:
initposs(sud);
for (unsigned r = 0; r < NDIGITS; ++r) {
for (unsigned c = 0; c < NDIGITS; ++c) {
unsigned val, n = 0;
do {
val = (unsigned)(rand() % NDIGITS);
++n;
if (n >= MAX_FILL_ATTEMPTS)
goto retry;
} while (update(sud, r, c, val) == NOT_ALLOWED);
}
}
for (unsigned r = 0; r < SIDELEN; ++r) {
for (unsigned c = 0; c < SIDELEN; ++c) {
if (rand() % FILLP_RCP == 0) {
assert(!sud->cells[r][c].det);
unsigned val, n = 0;
do {
val = (unsigned)(rand() % NDIGITS);
++n;
} while (update(sud, r, c, val) == NOT_ALLOWED);
}
/* Remove cells with probability of `1 / REMOVE_PROB_RECIP`. */
for (unsigned r = 0; r < NDIGITS; ++r) {
for (unsigned c = 0; c < NDIGITS; ++c) {
if (rand() % REM_PROB_DENOM < REM_PROB_NUMER)
clear(sud, r, c);
}
}
}
@ -66,14 +114,14 @@ enum update_res update(struct sudoku *sud, unsigned r, unsigned c, unsigned val)
return NOT_ALLOWED;
/* Update possible values of cells in same column. */
for (tr = 0; tr < SIDELEN; ++tr) {
for (tr = 0; tr < NDIGITS; ++tr) {
if (tr == r || sud->cells[tr][c].det)
continue;
sud->cells[tr][c].pvals[val] = false;
}
/* Update possible values of cells in same row. */
for (tc = 0; tc < SIDELEN; ++tc) {
for (tc = 0; tc < NDIGITS; ++tc) {
if (tc == c || sud->cells[r][tc].det)
continue;
sud->cells[r][tc].pvals[val] = false;
@ -99,7 +147,7 @@ enum update_res update(struct sudoku *sud, unsigned r, unsigned c, unsigned val)
void print(const struct sudoku *sud)
{
for (unsigned r = 0; r < SIDELEN; ++r) {
for (unsigned r = 0; r < NDIGITS; ++r) {
/*
* Print horizontal divider if on a segment boundary (but not
* at the start).
@ -107,7 +155,7 @@ void print(const struct sudoku *sud)
if (r != 0 && r % SEGLEN == 0)
puts("------+-------+------");
for (unsigned c = 0; c < SIDELEN; ++c) {
for (unsigned c = 0; c < NDIGITS; ++c) {
/*
* Print vertical divider if on a segment boundary (but
* not at the start).

3
sud.h
View File

@ -21,7 +21,6 @@
#include <stdbool.h>
#define SIDELEN 9
#define SEGLEN 3
#define NDIGITS 9
@ -34,7 +33,7 @@ struct cellstate {
};
struct sudoku {
struct cellstate cells[SIDELEN][SIDELEN];
struct cellstate cells[NDIGITS][NDIGITS];
};
enum update_res { NOT_ALLOWED, ALREADY_DET, OK };