[leetcode] 36. Valid Sudoku

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.

解法一：

数独的规则就是行、列、9个3*3的cell中不能出现重复的数字。思路是创建三个矩阵，row, col, cell, row[i][c]表示第i行中出现了数字c, col[j][c] 表示第j列出现了数字c, cell[k][c]表示第k个cell出现了数字c。每次去检查 row, col, cell中对应元素是不是有一个为true。

class Solution {public:    bool isValidSudoku(vector<vector<char>>& board) {        // check size        if (board.size()!=9) return false;        //////        vector<vector<bool> > row_flag(9,vector<bool>(9,false));        vector<vector<bool> > col_flag(9,vector<bool>(9,false));        vector<vector<bool> > cell_flag(9,vector<bool>(9,false));                for(int i=0; i<9; i++){            if (board[i].size()!=9)                return false;            for (int j=0; j<9; j++){                if (!validFill(board[i][j]))                    return false;                if (board[i][j] >= '1' && board[i][j] <= '9'){                    int val = board[i][j] - '1';                    if (row_flag[i][val] || col_flag[j][val] || cell_flag[3*(i/3)+j/3][val]) return false;                    row_flag[i][val] = true;                    col_flag[j][val] = true;                    cell_flag[3*(i/3)+j/3][val] = true;                }                            }                }                return true;            }        bool validFill(char c){        return c == '1' || c == '2' || c == '3' || c == '4' || c == '5' ||                c == '6' || c == '7' || c == '8' || c == '9' || c == '.';    }};