• leetcode 36. Valid Sudoku


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

    题目大意:验证一个数独是否是有效的:某一行/一列/3x3的子格子数字不能重复。 

     1 class Solution {
     2 public:
     3     bool isValidSudoku(vector<vector<char>>& board) {
     4         //map<int, map<char, int> > row, col, grid;
     5         vector<vector<int> > row(9, vector<int>(10, 0)), col(9, vector<int>(10, 0)), grid(9, vector<int>(10, 0));
     6         for (int i = 0; i < 9; i++) {
     7             for (int j = 0; j < 9; j++) {
     8                 char tmp = board[i][j];
     9                 if (tmp != '.') {
    10                     int num = tmp - '0';
    11                     if (row[i][num] != 0) {
    12                         return false;
    13                     } else {
    14                         row[i][num] = 1;
    15                     }
    16                     
    17                     if (col[j][num] != 0) {
    18                         return false;
    19                     } else {
    20                         col[j][num] = 1;
    21                     }
    22                     // 从左往右,从上至下,3x3格子分别从0-8编号。
    23                     if (grid[(i / 3) * 3 + (j / 3)][num] != 0) {
    24                         return false;
    25                     } else {
    26                         grid[(i / 3) * 3 + (j / 3)][num] = 1;
    27                     }
    28                 }
    29                 
    30             }
    31         }
    32         return true;
    33     }
    34 };
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  • 原文地址:https://www.cnblogs.com/qinduanyinghua/p/11521838.html
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