LeetCode刷题（87）～有效的数独

题目描述

判断一个 9x9 的数独是否有效。只需要根据以下规则，验证已经填入的数字是否有效即可。

数字 1-9 在每一行只能出现一次。
数字 1-9 在每一列只能出现一次。
数字 1-9 在每一个以粗实线分隔的 3x3 宫内只能出现一次。

上图是一个部分填充的有效的数独。

数独部分空格内已填入了数字，空白格用 ‘.’ 表示。

示例 1:

输入:
[
  ["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"]
]
输出: true

  
 

  
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示例 2:

输入:
[
  ["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"]
]
输出: false
解释: 除了第一行的第一个数字从 5 改为 8 以外，空格内其他数字均与 示例1 相同。 但由于位于左上角的 3x3 宫内有两个 8 存在, 因此这个数独是无效的。

  
 

  
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说明:

• 一个有效的数独（部分已被填充）不一定是可解的。
• 只需要根据以上规则，验证已经填入的数字是否有效即可。
• 给定数独序列只包含数字 1-9 和字符 ‘.’ 。
• 给定数独永远是 9x9 形式的。

解答 By 海轰

提交代码（暴力解法：利用哈希，每行、每列、每一块都检查）

 bool isValidSudoku(vector<vector<char>>& board) { unordered_map<char,int> m; for(int i=0;i<9;++i) { for(int j=0;j<9;++j) { ++m[board[i][j]]; if(board[i][j]!='.'&&m[board[i][j]]>1) return false; } m.clear(); } for(int i=0;i<9;++i) { for(int j=0;j<9;++j) { ++m[board[j][i]]; if(board[j][i]!='.'&&m[board[j][i]]>1) return false; } m.clear(); } for(int i=0;i<9;i+=3) { for(int j=0;j<9;j+=3) { for(int k=0;k<3;++k) { for(int q=0;q<3;++q) { ++m[board[i+k][j+q]]; if(board[i+k][j+q]!='.'&&m[board[i+k][j+q]]>1) return false; } } m.clear(); } } return true; }

  
 

  
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运行结果

解答

Demo【思路详解】

bool isValidSudoku(vector<vector<char>>& board) { int row[9][9]={0}; int col[9][9]={0}; int box[9][9]={0}; for(int i=0;i<9;++i) { for(int j=0;j<9;++j) { if(board[i][j]=='.') continue; int temp=board[i][j]-'0'; if(row[i][temp-1]) return false; if(col[j][temp-1]) return false; if(box[(i/3)*3+j/3][temp-1])  return false; row[i][temp-1]=1; col[j][temp-1]=1; box[(i/3)*3+j/3][temp-1]=1; } } return true; }

  
 

  
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运行结果

题目来源

来源：力扣（LeetCode）
链接：https://leetcode-cn.com/problems/valid-sudoku

文章来源: haihong.blog.csdn.net，作者：海轰Pro，版权归原作者所有，如需转载，请联系作者。

原文链接：haihong.blog.csdn.net/article/details/108171101