83 lines
2 KiB
C
83 lines
2 KiB
C
#include "internals.h"
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#include <stddef.h>
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#include "sudoku.h"
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static bool slice_line(bool possibilities[9][9][9], size_t x, size_t y) {
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bool changed = false;
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for (int n = 0; n < 9; ++n) {
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size_t line = -1;
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bool unique = true;
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for (size_t i = 3 * x; i < 3 * (x + 1); ++i) {
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for (size_t j = 3 * y; j < 3 * (y + 1); ++j) {
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if (!possibilities[i][j][n])
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continue;
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if (line >= 9)
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line = i;
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else if (line != i)
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unique = false;
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}
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}
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if (line >= 9 || !unique)
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continue;
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for (size_t c = 0; c < 9; ++c) {
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if ((c / 3) == y)
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continue;
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changed |= possibilities[line][c][n];
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possibilities[line][c][n] = false;
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}
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}
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return changed;
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}
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static bool slice_column(bool possibilities[9][9][9], size_t x, size_t y) {
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bool changed = false;
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for (int n = 0; n < 9; ++n) {
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size_t column = -1;
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bool unique = true;
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for (size_t i = 3 * x; i < 3 * (x + 1); ++i) {
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for (size_t j = 3 * y; j < 3 * (y + 1); ++j) {
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if (!possibilities[i][j][n])
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continue;
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if (column >= 9)
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column = j;
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else if (column != j)
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unique = false;
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}
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}
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if (column >= 9 || !unique)
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continue;
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for (size_t l = 0; l < 9; ++l) {
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if ((l / 3) == x)
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continue;
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changed |= possibilities[l][column][n];
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possibilities[l][column][n] = false;
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}
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}
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return changed;
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}
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bool slice_and_dice(bool possibilities[9][9][9]) {
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bool changed = false;
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for (size_t x = 0; x < 3; ++x) {
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for (size_t y = 0; y < 3; ++y) {
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changed |= slice_line(possibilities, x, y);
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changed |= slice_column(possibilities, x, y);
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}
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}
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return changed;
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}
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