面试经典150题——Day34

经典150题——Day34"/>

面试经典150题——Day34

文章目录

• • 一、题目
  • 二、题解

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

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

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;}
};