Word Ladder

注意各种数据结构的特点，删除的时候要注意遍历

public class Solution {
    public int ladderLength(String start, String end, HashSet<String> dict) {
        // IMPORTANT: Please reset any member data you declared, as
        // the same Solution instance will be reused for each test case.
        
        LinkedList<String> queue = new LinkedList<String>();
        int count = 1;
        queue.add(start);
        
        while(!queue.isEmpty())
        {
            if(queue.contains(end))
                return count;
            LinkedList<String> visited = new LinkedList<String>();
            while(!queue.isEmpty())
            {
                String tmp = queue.poll();
                for(int i=0;i < tmp.length(); i++)
                {
                    for(char j = 'a'; j <= 'z'; j++)
                    {
                        char[] mychar = tmp.toCharArray();
                        mychar[i] = j;
                        if(dict.contains(String.valueOf(mychar)))
                        {
                            dict.remove(String.valueOf(mychar)); 
                            visited.add(String.valueOf(mychar));
                        }
                        
                    }
                }
                
            }
            queue.addAll(visited);
            count++;
        }
        return 0;
    }
    
    private boolean isladder(String str1, String str2)
    {
        if(str1.length() != str2.length())
            return false;
        int count = 0;
        for(int i=0; i<str1.length(); i++)
            if(str1.charAt(i) != str2.charAt(i))
                count++;
        if(count == 1)
            return true;
        return false;
    }
}