leetcode-master/problems/0037.解数独.md

题目地址

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

思路

这道题目和之前递归的方式都不一样，这里相当于两层递归，之前的都是一层递归

C++代码

class Solution {
private:
bool backtracking(vector<vector<char>>& board) {
    for (int i = 0; i < board.size(); i++) {
        for (int j = 0; j < board[0].size(); j++) {
            if (board[i][j] != '.') continue;
            for (char k = '1'; k <= '9'; k++) {
                if (isValid(i, j, k, board)) {
                    board[i][j] = k;
                    if (backtracking(board)) return true;
                    board[i][j] = '.';
                }
            }
            return false;
        }
    }
    return true;

}
bool isValid(int row, int col, char val, vector<vector<char>>& board) {

    for (int i = 0; i < 9; i++) {
        if (board[row][i] == val) {
            return false;
        }
    }
    for (int j = 0; j < 9; j++) {
        if (board[j][col] == val) {
            return false;
        }

    }
    int startRow = (row / 3) * 3;
    int startCol = (col / 3) * 3;
    for (int i = startRow; i < startRow + 3; i++) {
        for (int j = startCol; j < startCol + 3; j++) {
            if (board[i][j] == val ) {
                return false;
            }
        }
    }
    return true;
}
public:
    void solveSudoku(vector<vector<char>>& board) {
        backtracking(board);
    }
};