题目:
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.
解题思路:分别对横向、纵向、小格子遍历即可。设一个set来表示已出现过的数字,并判断当前访问的数字是否在集合中(即判断是否已经出现过)。
代码:
class Solution { public: bool isValidSudoku(vector<vector<char> > &board) { set<char> visited; for(int i=0;i<9;i++){ visited.clear(); for(int j=0;j<9;j++){ if(visited.count(board[i][j])>0)return false; if(board[i][j]!='.'){ visited.insert(board[i][j]); } } } for(int i=0;i<9;i++){ visited.clear(); for(int j=0;j<9;j++){ if(visited.count(board[j][i])>0)return false; if(board[j][i]!='.'){ visited.insert(board[j][i]); } } } for(int i=0;i<3;i++){ for(int j=0;j<3;j++){ visited.clear(); for(int k=0;k<3;k++){ for(int l=0;l<3;l++){ if(visited.count(board[3*i+k][3*j+l])>0)return false; if(board[3*i+k][3*j+l]!='.'){ visited.insert(board[3*i+k][3*j+l]); } } } } } return true; } };