LeetCode36. Valid Sudoku（C++）

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.

Note:

• A Sudoku board (partially filled) could be valid but is not necessarily solvable.
• Only the filled cells need to be validated according to the mentioned rules.
• The given board contain only digits 1-9 and the character '.'.
• The given board size is always 9x9.

题目大意：判断数独是否有效，分行、列、小正方形进行判断

class Solution {
public:
    bool isValidSudoku(vector<vector<char>>& board) {
        bool visit[10];
        for(int i=0;i<9;i++){
            fill(visit,visit+10,false);
            for(int j=0;j<9;j++){
                if(isdigit(board[i][j])){
                    if(visit[board[i][j]-'0']==true)
                         return false;
                    else
                        visit[board[i][j]-'0']=true;
                }    
            }
        }  
        for(int i=0;i<9;i++){
            fill(visit,visit+10,false);
            for(int j=0;j<9;j++){
                if(isdigit(board[j][i])){
                    if(visit[board[j][i]-'0']==true)
                         return false;
                    else
                        visit[board[j][i]-'0']=true;
                }    
            }
         }
        for(int i=0;i<9;i+=3){
            for(int j=0;j<9;j+=3){
                fill(visit,visit+10,false);
                for(int p=0;p<3;p++){
                    for(int q=0;q<3;q++){
                         if(isdigit(board[i+p][j+q])&&visit[board[i+p][j+q]-'0']==true)
                            return false;
                        if(isdigit(board[i+p][j+q]))
                            visit[board[i+p][j+q]-'0']=true;
                    }
                }
            }
        }
        return true;                 
    }
};

优化一下，不额外遍历行和列，在判断每个小正方形的的时候把行和列顺带记录，这样整体只需要遍历一遍

class Solution {
public:
    bool isValidSudoku(vector<vector<char>>& board) {
        bool col[10][10],row[10][10],visit[10];
        fill(col[0],col[0]+10*10,false);
        fill(row[0],row[0]+10*10,false);
        for(int i=0;i<9;i+=3){
            for(int j=0;j<9;j+=3){
                fill(visit,visit+10,false);
                for(int p=0;p<3;p++){
                    for(int q=0;q<3;q++){
                         if(isdigit(board[i+p][j+q])&&(visit[board[i+p][j+q]-'0']==true||row[i+p][board[i+p][j+q]-'0']==true||col[j+q][board[i+p][j+q]-'0']==true))
                            return false;
                        if(isdigit(board[i+p][j+q])){
                             visit[board[i+p][j+q]-'0']=true;
                             row[i+p][board[i+p][j+q]-'0']=true;
                             col[j+q][board[i+p][j+q]-'0']=true;
                        }
                           
                    }
                }
            }
        }
        return true;                 
    }
};