LeetCode -- Word Ladder

public class Solution {
    public int LadderLength(string beginWord, string endWord, ISet<string> wordList) 
    {
        if(beginWord.Length == 1 )
    	{
    		return beginWord[0] != endWord[0] ? 2 : 0;
    	}
    	wordList.Remove(beginWord);
    	wordList.Add(endWord);
    	
    	var matchedWords = new HashSet<string>();
    	matchedWords.Add(beginWord);
    	
    	var found = false;
    	var result = new List<ISet<string>>(){matchedWords};
    	while(matchedWords.Count > 0 && !found){
    		var nextRound = new HashSet<string>();
    		foreach(var w in matchedWords){
    			if(w == endWord){
    				found = true;
    				break;
    			}
    			else{
    				var r = NextLadderWords(w, ref wordList);
    				foreach(var w1 in r){
    					nextRound.Add(w1);
    				}
    			}
    		}
    		
    		matchedWords = nextRound;
    		if(!found){
    			result.Add(nextRound);
    		}
    		
    	}
    	return found ? result.Count : 0;
    }


private ISet<string> NextLadderWords(string word,ref ISet<string> words){
	var ret = new HashSet<string>();
	var len = word.Length;
	for(var i = 0;i < len; i++){
		var c = (int)word[i];
		for(var j = ‘a‘; j <= ‘z‘; j++){
			if(c != j){				
				var newWord = word.ToCharArray();
				newWord[i] = (char)j;
				var s = new string(newWord);
				if(words.Contains(s)){
					ret.Add(s);
					words.Remove(s);
				}
			}
		}
	}
	
	return ret;
}




}

LeetCode -- Word Ladder

原文：http://blog.csdn.net/lan_liang/article/details/50144399