Leetcode：36. Valid Sudoku（JAVA）

【问题描述】

Determine if a Sudoku is valid, according to: Sudoku Puzzles - The Rules.

The Sudoku board could be partially filled, where empty cells are filled with the character '.'.

A partially filled sudoku which is valid.

Note:
A valid Sudoku board (partially filled) is not necessarily solvable. Only the filled cells need to be validated.

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【思路】

使用HashSet依次按行、列、小格检查。

【code】

public class Solution {    public boolean isValidSudoku(char[][] board) { Set<Character> set = new HashSet<Character>();// rowfor (int i = 0; i < 9; i++) {for (int j = 0; j < 9; j++) {if (board[i][j] == '.') {continue;}if (set.contains(board[i][j])) {return false;}set.add(board[i][j]);}set.clear();}// columnfor (int i = 0; i < 9; i++) {for (int j = 0; j < 9; j++) {if (board[j][i] == '.') {continue;}if (set.contains(board[j][i])) {return false;}set.add(board[j][i]);}set.clear();}// sub-gridfor (int i = 0; i < 9; i++) {for (int j = i / 3 * 3; j < i / 3 * 3 + 3; j++) {for (int k = (i % 3) * 3; k < (i % 3) * 3 + 3; k++) {if (board[j][k] == '.') {continue;}if (set.contains(board[j][k])) {return false;}set.add(board[j][k]);}}set.clear();}return true;    }}