文章目录
一、题目
36. Valid Sudoku
Determine if a 9 x 9 Sudoku board is valid. Only the filled cells need to be validated according to the following rules:
Each row must contain the digits 1-9 without repetition.
Each column must contain the digits 1-9 without repetition.
Each of the nine 3 x 3 sub-boxes of the grid must contain the digits 1-9 without repetition.
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.
Example 1:
Input: board =
[["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: board =
[["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.
Constraints:
board.length == 9
board[i].length == 9
board[i][j] is a digit 1-9 or '.'.
题目来源： leetcode
二、题解
我自己的笨方法
cpp
class Solution {
public:
bool isValidSudoku(vector<vector<char>>& board) {
unordered_map<char,int> map;
//遍历行
for(int i = 0;i < 9;i++){
//清除上行数据
map.clear();
for(int j = 0;j < 9;j++){
char c = board[i][j];
if(c != '.'){
if(map[c] == 0) map[c]++;
else if(map[c] == 1) return false;
}
}
}
//遍历列
for(int j = 0;j < 9;j++){
map.clear();
for(int i = 0;i < 9;i++){
char c = board[i][j];
if(c != '.'){
if(map[c] == 0) map[c]++;
else if(map[c] == 1) return false;
}
}
}
//遍历3x3宫格
for(int i = 0;i < 9;i += 3){
for(int j = 0;j < 9;j += 3){
map.clear();
for(int k = i;k < i + 3;k++){
for(int m = j;m < j + 3;m++){
char c = board[k][m];
if(c != '.'){
if(map[c] == 0) map[c]++;
else if(map[c] == 1) return false;
}
}
}
}
}
return true;
}
};答案的好方法
cpp
class Solution {
public:
bool isValidSudoku(vector<vector<char>>& board) {
int rows[9][9];
int columns[9][9];
int subboxes[3][3][9];
memset(rows,0,sizeof(rows));
memset(columns,0,sizeof(columns));
memset(subboxes,0,sizeof(subboxes));
for (int i = 0; i < 9; i++) {
for (int j = 0; j < 9; j++) {
char c = board[i][j];
if (c != '.') {
int index = c - '0' - 1;
rows[i][index]++;
columns[j][index]++;
subboxes[i / 3][j / 3][index]++;
if (rows[i][index] > 1 || columns[j][index] > 1 || subboxes[i / 3][j / 3][index] > 1) {
return false;
}
}
}
}
return true;
}
};