0036_Valid Sudoku

最新推荐文章于 2021-03-02 12:20:25 发布

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最新推荐文章于 2021-03-02 12:20:25 发布

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分类专栏： LeetCode

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本文介绍了一种通过检查已填充的数字是否违反数独规则来验证数独有效性的方法。文章详细展示了如何利用HashSet来判断行、列及子格内的数字是否重复。

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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 ‘.’.

数独例子
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.

JAVA

方法一

并不知道如何来判断是不是一个可用的数独，只能尝试一下判断已经填写的数字中是否有不满足数独规则的，分别判断行、列、子格。没想到竟然过了，就是效率不高，在3/4左右。。

public class Solution {
    static int MAXSIZE = 9;
    static int SUBBOXSIZE = 3;
    public boolean isValidSudoku(char[][] board) {
        if (board.length != MAXSIZE || board[0].length != MAXSIZE){
            return false;
        }

        for (int i = 0; i < MAXSIZE; ++i){
            if (!judgeRow(board,i)){
                return false;
            }
        }

        for (int i = 0; i < MAXSIZE; ++i){
            if (!judgeColumn(board,i)){
                return false;
            }
        }

        for (int i = 0; i < MAXSIZE; i += 3){
            for(int j = 0; j < MAXSIZE; j += 3){
                if (!judgeSubBox(board,i,j)){
                    return false;
                }
            }
        }
        return true;
    }
    public boolean judgeRow(char[][] board,int row){
        HashSet<Character> used = new HashSet<Character>();
        for(int i = 0; i < MAXSIZE; ++i){
            if(board[row][i] != '.' && used.contains(board[row][i])){
                return false;
            }else{
                used.add(board[row][i]);
            }
        }
        return true;
    }

    public boolean judgeColumn(char[][] board,int column){
        HashSet<Character> used = new HashSet<Character>();
        for(int i = 0; i < MAXSIZE; ++i){
            if(board[i][column] != '.' && used.contains(board[i][column])){
                return false;
            }else{
                used.add(board[i][column]);
            }
        }
        return true;
    }

    public boolean judgeSubBox(char[][] board,int row,int column){
        HashSet<Character> used = new HashSet<Character>();
        for(int i = 0; i < SUBBOXSIZE; ++i){
            for (int j = 0; j < SUBBOXSIZE; ++j){
                if(board[row + i][column + j] != '.' && used.contains(board[row + i][column + j])){
                    return false;
                }else{
                    used.add(board[row + i][column + j]);
                }
            }
        }
        return true;
    }
}