# [LeetCode] 36. Valid Sudoku 验证数独

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 1-9without 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 1-9and the character '.'.
• The given board size is always 9x9.

class Solution {
public:
bool isValidSudoku(vector<vector<char>>& board) {
vector<vector<bool>> rowFlag(9, vector<bool>(9));
vector<vector<bool>> colFlag(9, vector<bool>(9));
vector<vector<bool>> cellFlag(9, vector<bool>(9));
for (int i = 0; i < 9; ++i) {
for (int j = 0; j < 9; ++j) {
if (board[i][j] == '.') continue;
int c = board[i][j] - '1';
if (rowFlag[i][c] || colFlag[c][j] || cellFlag[3 * (i / 3) + j / 3][c]) return false;
rowFlag[i][c] = true;
colFlag[c][j] = true;
cellFlag[3 * (i / 3) + j / 3][c] = true;
}
}
return true;
}
};

class Solution {
public:
bool isValidSudoku(vector<vector<char>>& board) {
unordered_set<string> st;
for (int i = 0; i < 9; ++i) {
for (int j = 0; j < 9; ++j) {
if (board[i][j] == '.') continue;
string t = "(" + to_string(board[i][j]) + ")";
string row = to_string(i) + t, col = t + to_string(j), cell = to_string(i / 3) + t + to_string(j / 3);
if (st.count(row) || st.count(col) || st.count(cell)) return false;
st.insert(row);
st.insert(col);
st.insert(cell);
}
}
return true;
}
};

Github 同步地址：

https://github.com/grandyang/leetcode/issues/36

Sudoku Solver

https://leetcode.com/problems/valid-sudoku/

https://leetcode.com/problems/valid-sudoku/discuss/15450/Shared-my-concise-Java-code

https://leetcode.com/problems/valid-sudoku/discuss/15472/Short%2BSimple-Java-using-Strings

LeetCode All in One 题目讲解汇总(持续更新中...)

posted @ 2015-04-13 07:05  Grandyang  阅读(20317)  评论(4编辑  收藏  举报