LeetCode: 36. Valid Sudoku

LeetCode: 36. Valid Sudoku

题目描述

Determine if a Sudoku is valid, according to: ​​Sudoku Puzzles - The Rules​​.

The Sudoku board could be partially filled, where empty cells are filled with the character ‘.’.

A partially filled sudoku which is valid.

Note:

A valid Sudoku board (partially filled) is not necessarily solvable. Only the filled cells need to be validated.

大意是说: 判断给定的矩阵是否满足每行、每列、每个3*3的小矩阵中没有重复的数字(1-9)。

解题思路

只需要用一个hash表记录每行每列每个小矩阵中出现过的 1-9即可。这里我用一个 int 的0-8位的值来表示数字1-9是否出现过, 当数字i出现时, 就将第i-1位标记为1。

AC源码

class Solution {
public:
    bool isValidSudoku(vector<vector<char>>& board) {
        int row[9] = {0};
        int column[9] = {0};
        int rect[9] = {0};

        for(int i = 0; i < board.size(); ++i)
        {
            for(int j = 0; j < board[i].size(); ++j){
                if(board[i][j] != '.')
                {
                    int value = 1 << (board[i][j] - '0' - 1);
                    if(row[i] & value) return false;
                    else row[i] |= value;

                    if(column[j] & value) return false;
                    else column[j] |= value;

                    int rectIdx = i/3*3 + j/3;
                    if(rect[rectIdx]&value) return false;
                    else rect[rectIdx] |= value;
                }
            }
        }
        return true;
    }
};