LeetCode 36. Valid Sudoku

Posted 2020-08-09

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.

首先你要弄懂数独的含义， 就是每行每列最多只能有一个1-9之间的数字，以及上面图中画出的每个小3*3方格也只能最多有一个1-9之间的数字

 

为了统计每行每列以及每个小3*3方格内数字的个数，我设置了三个向量，同时我们恰好可以用向量的下标来对应数字，用向量的值来统计1-9出现

的次数，如果出现的次数大于1，就说明不是数独

class Solution {
public:
    bool isValidSudoku(vector<vector<char>>& board) {
        vector<int> rowvec(board.size()+1,0);
        vector<int> columnvec(board.size()+1,0);
        vector<int> smallvec(board.size()+1,0);
        vector<int> vec(board.size()+1, 0);
        for (int i = 0;i < board.size();++i)
        {
            for (int j = 0;j < board.size();++j)
            {
                if (board[i][j] != ‘.‘)
                {
                    if(++rowvec[board[i][j]-48]>1)return false;
                    
                }
                    
                if (board[j][i] != ‘.‘)
                {
                    if(++columnvec[board[j][i]-48]>1)return false;
                    
                }
                if (i % 3 == 0 && j % 3 == 0)
                {
                    for(int ii=i;ii<i+3;++ii)
                        for (int jj = j;jj < j + 3;++jj)
                        {
                            if (board[ii][jj] != ‘.‘)
                                if (++smallvec[board[ii][jj] - 48] > 1)return false;
                        }
                }
                smallvec=vec;
            }
            rowvec = vec;
            columnvec = vec;
        }
        return true;
    }
};