sudoku: solver: add last remaining heuristic

This commit is contained in:
Bruno BELANYI 2020-12-22 17:39:38 +01:00
parent 18bb94836e
commit b17cb8d84c
4 changed files with 79 additions and 0 deletions

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@ -11,6 +11,7 @@ project(
sources = [ sources = [
'src/constraints.c', 'src/constraints.c',
'src/main.c', 'src/main.c',
'src/solver/last_remaining.c',
'src/solver/single_occurence.c', 'src/solver/single_occurence.c',
'src/solver/solve.c', 'src/solver/solve.c',
'src/solver/update_sets.c', 'src/solver/update_sets.c',

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@ -7,5 +7,6 @@ struct sudoku;
bool update_sets(const struct sudoku *grid, bool possibilities[9][9][9]); bool update_sets(const struct sudoku *grid, bool possibilities[9][9][9]);
bool single_occurrence(struct sudoku *grid, bool possibilities[9][9][9]); bool single_occurrence(struct sudoku *grid, bool possibilities[9][9][9]);
bool last_remaining(struct sudoku *grid);
#endif /* !INTERNALS_H */ #endif /* !INTERNALS_H */

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@ -0,0 +1,76 @@
#include "internals.h"
#include <stddef.h>
#include "sudoku.h"
static bool last_line(struct sudoku *grid, size_t i, size_t j) {
size_t numbers = 9 * 10 / 2; // Sum from 1 to 9
size_t remaining = 9;
for (size_t c = 0; c < 9; ++c) {
if (c == j)
continue;
numbers -= grid->grid[i][c];
remaining -= grid->grid[i][c] != 0;
}
if (remaining != 1)
return false;
grid->grid[i][j] = numbers;
return true;
}
static bool last_column(struct sudoku *grid, size_t i, size_t j) {
size_t numbers = 9 * 10 / 2; // Sum from 1 to 9
size_t remaining = 9;
for (size_t l = 0; l < 9; ++l) {
if (l == i)
continue;
numbers -= grid->grid[l][j];
remaining -= grid->grid[l][j] != 0;
}
if (remaining != 1)
return false;
grid->grid[i][j] = numbers;
return true;
}
static bool last_square(struct sudoku *grid, size_t i, size_t j) {
const size_t x = i / 3;
const size_t y = j / 3;
size_t numbers = 9 * 10 / 2; // Sum from 1 to 9
size_t remaining = 9;
for (size_t l = 3 * x; l < 3 * (x + 1); ++l) {
for (size_t c = 3 * y; c < 3 * (y + 1); ++c) {
if ((l == i) && (c == j))
continue;
numbers -= grid->grid[l][c];
remaining -= grid->grid[l][c] != 0;
}
}
if (remaining != 1)
return false;
grid->grid[i][j] = numbers;
return true;
}
bool last_remaining(struct sudoku *grid) {
bool changed = false;
for (size_t i = 0; i < 9; ++i) {
for (size_t j = 0; j < 9; ++j) {
if (grid->grid[i][j] != 0)
continue;
changed |= last_line(grid, i, j) || last_column(grid, i, j)
|| last_square(grid, i, j);
}
}
return changed;
}

View file

@ -29,6 +29,7 @@ bool solve(struct sudoku *grid) {
changed |= update_sets(grid, possibilities); changed |= update_sets(grid, possibilities);
changed |= single_occurrence(grid, possibilities); changed |= single_occurrence(grid, possibilities);
changed |= last_remaining(grid);
} while (changed); } while (changed);
return solved(grid); return solved(grid);