32 - Valid Sudoku_anti-sudoku csdn-优快云博客

本文介绍了一种通过记录行、列及区块内数字出现次数的方法来判断数独是否有效。利用多个二维数组跟踪1到9这些数字在数独中的分布情况，确保每个数字在同一行、同一列和同一区块内不重复出现。

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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.

solution：空间换时间，设置多个二维数组分别记录横，纵，块中九个数字的出现次数，若重复出现则报错，反之该数独是valid的。

PS: 还需要判断数是否在1-9之间，若超出该范围也是错误的。

class Solution {
public:
    bool isValidSudoku(vector<vector<char> > &board) {
        // Note: The Solution object is instantiated only once and is reused by each test case.
        int si = board[0].size();
        if(si <= 0)
            return false;
        
        vector< vector<bool> >rows(si,vector<bool>(si,false));
        vector< vector<bool> >cols(si,vector<bool>(si,false));
        vector< vector<bool> >blocks(si,vector<bool>(si,false));
        
        for(int row = 0; row < si; row++)
        {
            for(int col = 0; col < si; col++)
            {
                char temp = board[ row ][ col ];
                if(temp == '.')
                    continue;
                int num = temp - '1';
                if( rows[ row ][ num ] || cols[ col ][ num ] || blocks[ col/3 + row - row % 3 ][ num ] )
                    return false;
                
                rows[ row ][ num ] = true;
                cols[ col ][ num ] = true;
                blocks[ col/3 + row - row % 3 ][ num ] = true;
            }
        }
        return true;
    }
};