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| package cn.edu.xidian.sselab.hashtable; import java.util.HashSet; import java.util.Set; /** * * @author zhiyong wang * title: Valid Sudoku * content: * 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. * */ public class ValidSudoku { //参考了大牛的解法，自己拉下了每个小九方格也要进行比较，最大时间复杂度O(n^4) public boolean isValidSudoku(char[][] board){ //先比较一横行或者一竖列 for(int i=0;i<9;i++){ if(!isValidSudokus(board, 0, i, 8, i)) return false; if(!isValidSudokus(board, i, 0, i, 8)) return false; } //然后比较每个小九方格 for(int i=0;i<3;i++){ for(int j=0;j<3;j++){ if(!isValidSudokus(board, i*3, j*3, i*3+2, j*3+2)) return false; } } return true; } //将比较的过程提炼了出来 //这里有个index.add，如果存在返回false，不存在返回true public boolean isValidSudokus(char[][] board, int x1, int y1, int x2, int y2){ Set index = new HashSet(); for(int i=x1;i<=x2;i++){ for (int j=y1;j<=y2;j++){ if(board[i][j] != ‘.‘){ if(!index.add(board[i][j])) return false; } } } return true; } } |
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原文地址：http://www.cnblogs.com/wzyxidian/p/5154856.html
