Leetcode 36. Valid Sudoku（附上ASCII表）

Determine if a 9x9 Sudoku board is valid. Only the filled cells need to be validated according to the following rules:

1. Each row must contain the digits 1-9 without repetition.
2. Each column must contain the digits 1-9 without repetition.
3. Each of the 9 3x3 sub-boxes of the grid must contain the digits 1-9 without repetition.

A partially filled sudoku which is valid.

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

Example 1:

Input:
[
  ["5","3",".",".","7",".",".",".","."],
  ["6",".",".","1","9","5",".",".","."],
  [".","9","8",".",".",".",".","6","."],
  ["8",".",".",".","6",".",".",".","3"],
  ["4",".",".","8",".","3",".",".","1"],
  ["7",".",".",".","2",".",".",".","6"],
  [".","6",".",".",".",".","2","8","."],
  [".",".",".","4","1","9",".",".","5"],
  [".",".",".",".","8",".",".","7","9"]
]
Output: true

Example 2:

Input:
[
  ["8","3",".",".","7",".",".",".","."],
  ["6",".",".","1","9","5",".",".","."],
  [".","9","8",".",".",".",".","6","."],
  ["8",".",".",".","6",".",".",".","3"],
  ["4",".",".","8",".","3",".",".","1"],
  ["7",".",".",".","2",".",".",".","6"],
  [".","6",".",".",".",".","2","8","."],
  [".",".",".","4","1","9",".",".","5"],
  [".",".",".",".","8",".",".","7","9"]
]
Output: false
Explanation: Same as Example 1, except with the 5 in the top left corner being 
    modified to 8. Since there are two 8's in the top left 3x3 sub-box, it is invalid.

题目链接：https://leetcode.com/problems/valid-sudoku/

思路：横向检查9次，竖向检查9次，检查9个9宫格

class Solution {
public:
    bool isValidSudoku(vector<vector<char>>& board) {
        int a[100]={0};
        for(int i=0;i<9;i++)
        {
            memset(a,0,sizeof(a));
            for(int j=0;j<9;j++)
            {
                if(board[i][j]>='0'&&board[i][j]<='9')
                {
                    a[board[i][j]]++;
                    if(a[board[i][j]]>1)
                    {
                        return false;
                    }
                }
            }
        }
        for(int i=0;i<9;i++)
        {
            memset(a,0,sizeof(a));
            for(int j=0;j<9;j++)
            {
                if(board[j][i]>='0'&&board[j][i]<='9')
                {
                    a[board[j][i]]++;
                    if(a[board[j][i]]>1)
                    {
                        return false;
                    }
                }
            }
        }
        for(int r=0;r<9;r+=3)
        {
            for(int c=0;c<9;c+=3)
            {
                memset(a,0,sizeof(a));
                for(int i=r;i<r+3;i++)
                {
                    for(int j=c;j<c+3;j++)
                    {
                        if(board[j][i]>='0'&&board[j][i]<='9')
                        {
                            a[board[j][i]]++;
                            if(a[board[j][i]]>1)
                            {
                                return false;
                            }
                        }
                    }
                }
            }
        }
        return true;
    }
};