19.2.3 [LeetCode 37] Sudoku Solver

Write a program to solve a Sudoku puzzle by filling the empty cells.

A sudoku solution must satisfy all of the following rules:

1. Each of the digits 1-9 must occur exactly once in each row.
2. Each of the digits 1-9 must occur exactly once in each column.
3. Each of the the digits 1-9 must occur exactly once in each of the 9 3x3sub-boxes of the grid.

Empty cells are indicated by the character '.'.

A sudoku puzzle...

...and its solution numbers marked in red.

Note:

• The given board contain only digits 1-9 and the character '.'.
• You may assume that the given Sudoku puzzle will have a single unique solution.
• The given board size is always 9x9.

class Solution {
public:
    bool solvefromone(int x, int y, vector<vector<char>>&board) {
        bool used[10] = { false };
        for (int i = 0; i < 9; i++) {
            if (board[x][i] != '.')
                used[board[x][i] - '0'] = true;
            if (board[i][y] != '.')
                used[board[i][y] - '0'] = true;
        }
        int xs = x / 3 * 3, xe = xs + 2, ys = y / 3 * 3, ye = ys + 2;
        for (int i = xs; i <= xe; i++)
            for (int j = ys; j <= ye; j++)
                if (board[i][j] != '.')
                    used[board[i][j] - '0'] = true;
        int nextx=x, nexty=y;
        for(int i=y+1;i<9;i++)
            if (board[x][i] == '.') {
                nextx = x; nexty = i;
                break;
            }
        if (nexty == y) {
            for (int i = x + 1; i < 9; i++) {
                for (int j = 0; j < 9; j++) {
                    if (board[i][j] == '.') {
                        nextx = i; nexty = j;
                        break;
                    }
                }
                if (nextx != x)break;
            }
        }
        for(int i=1;i<=9;i++)
            if (!used[i]) {
                board[x][y] = i + '0';
                if (nextx == x && nexty == y)
                    return true;
                if (solvefromone(nextx, nexty, board))
                    return true;
            }
        board[x][y] = '.';
        return false;
    }
    void solveSudoku(vector<vector<char>>& board) {
        for (int i = 0; i < 9; i++)
            for (int j = 0; j < 9; j++)
                if (board[i][j] == '.')
                    solvefromone(i, j, board);
    }
};

暴力深搜，手误WA得有点不爽

好冷啊

孤单弱小无助