hashtable

hashmap.put(key,value);
hashmap.get(key) is value;
hashmap.containsKey(key);
hashset.add(value);
hashset.contains(value);
http://blog.csdn.net/sbitswc/article/details/48997977
word pattern
public boolean wordPattern(String pattern, String str) {
        String[] strs = str.split(" ");
        if(pattern.length() != strs.length) return false;
        Map<Character, String> map = new HashMap<Character, String>();
        for(int i=0;i<pattern.length();i++) {
            if(!map.containsKey(pattern.charAt(i))) {
                if(map.containsValue(strs[i])) return false;
                map.put(pattern.charAt(i), strs[i]);
            }else {
                if(strs[i].equals(map.get(pattern.charAt(i)))) continue;
                else return false;
            }
        }
        return true;
    }
http://blog.csdn.net/linhuanmars/article/details/20748171
validate sudoku
public boolean isValidSudoku(char[][] board) {
    if(board==null || board.length!=9 || board[0].length!=9)
        return false;
    for(int i=0;i<9;i++)
    {
        boolean[] map = new boolean[9];
        for(int j=0;j<9;j++)
        {
            if(board[i][j] != '.')
            {
                if(map[(int)(board[i][j]-'1')])
                {
                    return false;
                }
                map[(int)(board[i][j]-'1')] = true;
            }
        }
    }
    for(int j=0;j<9;j++)
    {
        boolean[] map = new boolean[9];
        for(int i=0;i<9;i++)
        {
            if(board[i][j] != '.')
            {
                if(map[(int)(board[i][j]-'1')])
                {
                    return false;
                }
                map[(int)(board[i][j]-'1')] = true;
            }
        }
    }
    for(int block=0;block<9;block++)
    {
        boolean[] map = new boolean[9];
        for(int i=block/3*3;i<block/3*3+3;i++)
        {
            for(int j=block%3*3;j<block%3*3+3;j++)
            {
                if(board[i][j] != '.')
                {
                   if(map[(int)(board[i][j]-'1')])
                   {
                      return false;
                   }
                   map[(int)(board[i][j]-'1')] = true;
                }
            }
        }
    }
    return true;
}