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Diffstat (limited to 'sudoku_solver.c')
-rw-r--r-- | sudoku_solver.c | 69 |
1 files changed, 69 insertions, 0 deletions
diff --git a/sudoku_solver.c b/sudoku_solver.c new file mode 100644 index 0000000..88ccc01 --- /dev/null +++ b/sudoku_solver.c @@ -0,0 +1,69 @@ +// 37. Sudoku Solver +#include "leetcode.h" + +/* + * write a program to solve a sudoku puzzle by filling the empty cells. a sudoku + * solution must satisfy all of the following rules. each of the digits '1-9' + * must occur exactly once in each row, each of the digits '1-9', must occur + * exactly once in each column, and each of the digits '1-9' must occur exactly + * once in each of the 9 3x3 sub-boxes of the grid. the '.' character indicates + * empty cells. + */ + +bool solve(char **board, bool row[9][9], bool col[9][9], bool grid[9][9], int r, + int c) { + if (r == 9) + return true; + int next_r = c == 8 ? r + 1 : r; + int next_c = c == 8 ? 0 : c + 1; + if (board[r][c] != '.') + return solve(board, row, col, grid, next_r, next_c); + int grid_idx = (r / 3) * 3 + (c / 3); + for (int i = 0; i < 9; i++) { + if (!row[r][i] && !col[c][i] && !grid[grid_idx][i]) { + board[r][c] = '1' + i; + row[r][i] = col[c][i] = grid[grid_idx][i] = true; + if (solve(board, row, col, grid, next_r, next_c)) + return true; + board[r][c] = '.'; + row[r][i] = col[c][i] = grid[grid_idx][i] = false; + } + } + return false; +} + +void solveSudoku(char **board, int boardSize, int *boardColSize) { + if (boardSize != 9 || *boardColSize != 9) + return; + bool row[9][9] = {false}; + bool col[9][9] = {false}; + bool grid[9][9] = {false}; + for (int i = 0; i < 9; i++) + for (int j = 0; j < 9; j++) + if (board[i][j] != '.') { + int num = board[i][j] - '1'; + if (num < 0 || num >= 9) + return; + row[i][num] = col[j][num] = true; + grid[(i / 3) * 3 + (j / 3)][num] = true; + } + solve(board, row, col, grid, 0, 0); +} + +int main() { + char *board[] = {{"5", "3", ".", ".", "7", ".", ".", ".", "."}, + {"6", ".", ".", "1", "9", "5", ".", ".", "."}, + {".", "9", "8", ".", ".", ".", ".", "6", "."}, + {"8", ".", ".", ".", "6", ".", ".", ".", "3"}, + {"4", ".", ".", "8", ".", "3", ".", ".", "1"}, + {"7", ".", ".", ".", "2", ".", ".", ".", "6"}, + {".", "6", ".", ".", ".", ".", "2", "8", "."}, + {".", ".", ".", "4", "1", "9", ".", ".", "5"}, + {".", ".", ".", ".", "8", ".", ".", "7", "9"}}; + solveSudoku((char **)board, ARRAY_SIZE(board), ARRAY_SIZE(board[0])); + for (int i = 0; i < ARRAY_SIZE(board); i++) { + for (int j = 0; j < ARRAY_SIZE(board[0]); j++) + printf("%c ", board[i][j]); + printf("\n"); + } +} |