leetcode-----37. 解数独

• 链接：https://leetcode-cn.com/problems/sudoku-solver/

代码

class Solution {
public:
    bool row[9][9], col[9][9], cell[3][3][9];

    void solveSudoku(vector<vector<char>>& board) {
        memset(row, 0, sizeof row);
        memset(col, 0, sizeof col);
        memset(cell, 0, sizeof cell);

        for (int i = 0; i < 9; ++i) {
            for (int j = 0 ; j < 9; ++j) {
                if (board[i][j] != '.') {
                    int t = board[i][j] - '1';
                    row[i][t] = col[j][t] = cell[i / 3][j / 3][t] = true;
                }
            }
        }    
        dfs(board, 0, 0);
    }

    bool dfs(vector<vector<char>>& board, int x, int y) {
        if (y == 9) ++x, y = 0;
        if (x == 9) return true;
        if (board[x][y] != '.') return dfs(board, x, y + 1);
        for (int i = 0; i < 9; ++i) {
            if (!row[x][i] && !col[y][i] && !cell[x / 3][y / 3][i]) {
                board[x][y] = i + '1';
                row[x][i] = col[y][i] = cell[x / 3][y / 3][i] = true;
                if (dfs(board, x, y + 1)) return true;
                board[x][y] = '.';
                row[x][i] = col[y][i] = cell[x / 3][y / 3][i] = false;
            }
        }
        return false;
    }

};