77 lines
1.8 KiB
C
77 lines
1.8 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 last_line(struct sudoku *grid, size_t i, size_t j) {
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size_t numbers = 9 * 10 / 2; // Sum from 1 to 9
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size_t remaining = 9;
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for (size_t c = 0; c < 9; ++c) {
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if (c == j)
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continue;
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numbers -= grid->grid[i][c];
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remaining -= grid->grid[i][c] != 0;
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}
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if (remaining != 1)
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return false;
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grid->grid[i][j] = numbers;
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return true;
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}
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static bool last_column(struct sudoku *grid, size_t i, size_t j) {
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size_t numbers = 9 * 10 / 2; // Sum from 1 to 9
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size_t remaining = 9;
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for (size_t l = 0; l < 9; ++l) {
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if (l == i)
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continue;
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numbers -= grid->grid[l][j];
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remaining -= grid->grid[l][j] != 0;
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}
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if (remaining != 1)
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return false;
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grid->grid[i][j] = numbers;
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return true;
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}
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static bool last_square(struct sudoku *grid, size_t i, size_t j) {
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const size_t x = i / 3;
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const size_t y = j / 3;
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size_t numbers = 9 * 10 / 2; // Sum from 1 to 9
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size_t remaining = 9;
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for (size_t l = 3 * x; l < 3 * (x + 1); ++l) {
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for (size_t c = 3 * y; c < 3 * (y + 1); ++c) {
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if ((l == i) && (c == j))
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continue;
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numbers -= grid->grid[l][c];
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remaining -= grid->grid[l][c] != 0;
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}
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}
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if (remaining != 1)
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return false;
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grid->grid[i][j] = numbers;
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return true;
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}
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bool last_remaining(struct sudoku *grid) {
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bool changed = false;
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for (size_t i = 0; i < 9; ++i) {
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for (size_t j = 0; j < 9; ++j) {
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if (grid->grid[i][j] != 0)
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continue;
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changed |= last_line(grid, i, j) || last_column(grid, i, j)
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|| last_square(grid, i, j);
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}
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}
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return changed;
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}
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