[LeetCode]36. Valid Sudoku

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 ‘.’.

Note:

A valid Sudoku board (partially filled) is not necessarily solvable. Only the filled cells need to be validated.

分析

这个题目没有什么太多的技巧啦，逐行扫描各行，用一个几个set来记录当前行出现的数字；同样方式扫描各列；然后扫描各个方块。

源码

class Solution {
public:
bool isValidSudoku(vector<vector<char>>& board) {
for(int row = 0; row < board.size(); row++) {
unordered_set<char> rowSet;
unordered_set<char> colSet;
for(int col = 0; col < board[row].size(); col++) {
// 同一行检查
if(board[row][col] != '.' && rowSet.find(board[row][col]) != rowSet.end()) return false;
else rowSet.insert(board[row][col]);

// 同一列检查
if(board[col][row] != '.' && colSet.find(board[col][row]) != colSet.end()) return false;
else colSet.insert(board[col][row]);

}
}

// 检查正方形
for(int index = 0; index < 9; index++) {
unordered_set<char> set;
for(int row = 0; row < 3; row++) {
for(int col = 0; col < 3; col++) {
char c = board[3 * (index / 3) + row][3 * (index % 3) + col];
if(c != '.' && set.find(c) != set.end()) return false;
else set.insert(c);
}
}
}
return true;
}
};