Total Accepted: 24574Total Submissions: 90344

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.

[分析]

每行,每列,每个square,都不能重复.用 SET 记录即可.

[CODE]

public class Solution {
    public boolean isValidSudoku(char[][] board) {
        List<Set<Character>> rl = new ArrayList<Set<Character>>();
        List<Set<Character>> cl = new ArrayList<Set<Character>>();
        List<Set<Character>> sl = new ArrayList<Set<Character>>();
        
        for(int i=0; i<9; i++) {
            rl.add(new HashSet<Character>());
            cl.add(new HashSet<Character>());
            sl.add(new HashSet<Character>());
        }
        int n = board.length;
        for(int i=0; i<n; i++) {
            for(int j=0; j<n; j++) {
                char c = board[i][j];
                if(c=='.') continue;
                else if(rl.get(i).contains(c) || cl.get(j).contains(c) || sl.get(i/3*3 + j/3).contains(c)) return false;
                else {
                    rl.get(i).add(c);
                    cl.get(j).add(c);
                    sl.get(i/3*3+j/3).add(c);
                }
            }
        }
        
        return true;
    }
}

leetcode 36: Valid Sudoku