原题
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
示例1:
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。
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。
解法
思想
行、列、宫分别分配一个哈希集记录出现的数字。
代码
class Solution {
char[][] globalBoard;
//行:0-8,列:9-17,宫:18-26
Set<Character>[] sets = new Set[27];
public boolean isValidSudoku(char[][] board) {
for(int i = 0;i<27;i++){
sets[i] = new HashSet<>();
}
globalBoard = board;
for(int x = 0 ; x < 9 ; x ++){
for(int y = 0;y<9;y++){
if(isValidSingle(x,y)==false) return false;
}
}
return true;
}
public boolean isValidSingle(int x,int y){
if(globalBoard[x][y]=='.') return true;
if(sets[x].contains(globalBoard[x][y])) return false;
sets[x].add(globalBoard[x][y]);
if(sets[9+y].contains(globalBoard[x][y])) return false;
sets[9+y].add(globalBoard[x][y]);
if(sets[18+y/3*3+x/3].contains(globalBoard[x][y])) return false;
sets[18+y/3*3+x/3].add(globalBoard[x][y]);
return true;
}
}
原创文章,作者:彭晨涛,如若转载,请注明出处:https://www.codetool.top/article/leetcode36-%e6%9c%89%e6%95%88%e7%9a%84%e6%95%b0%e7%8b%ac/