【BFS】【迭代】【Java】Leetcode 单词接龙_单词接龙 最长 算法 java

给定两个单词（beginWord 和 endWord）和一个字典，找到从 beginWord 到 endWord 的最短转换序列的长度。转换需遵循如下规则：
 
每次转换只能改变一个字母。
转换过程中的中间单词必须是字典中的单词。
说明:
 
如果不存在这样的转换序列，返回 0。
所有单词具有相同的长度。
所有单词只由小写字母组成。
字典中不存在重复的单词。
你可以假设 beginWord 和 endWord 是非空的，且二者不相同。
示例 1:
 
输入:
beginWord = "hit",
endWord = "cog",
wordList = ["hot","dot","dog","lot","log","cog"]
 
输出: 5
 
解释: 一个最短转换序列是 "hit" -> "hot" -> "dot" -> "dog" -> "cog",
     返回它的长度 5。
示例 2:
 
输入:
beginWord = "hit"
endWord = "cog"
wordList = ["hot","dot","dog","lot","log"]
 
输出: 0
 
解释: endWord "cog" 不在字典中，所以无法进行转换。

import java.util.*;
class BuNode{ //节点
    StringBuffer s;
    int deeps=1;
    public BuNode(){
 
    }
    public BuNode(StringBuffer s){
        this.s=s;
    }
}
public class ChangeWords {
    public static void main(String[] args) {
        String begin="hit";
        String end="cog";
        ArrayList list=new ArrayList();
        list.add("hot");
        list.add("dot");
        list.add("dog");
        list.add("lot");
        list.add("log");
        list.add("cog");
        list.add("hit");
        int a=chage(begin,end,list);
        System.out.println("deeps"+a);
 
    }
    public static int chage(String begin, String end, ArrayList list){
        StringBuffer buffer=new StringBuffer();
        buffer.append(begin);
        Queue<BuNode> queue=new LinkedList();
        BuNode buNode=new BuNode(buffer);
        queue.add(buNode);
        ArrayList list1=new ArrayList();
        int deeps=0;
        String word[]={"a","b","c","d","e","f","g","h","i","g","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z"};
        while (!queue.isEmpty()){
            BuNode buNode1=  queue.poll();
            if (buNode1.s.toString().equals(end)){
                deeps=buNode1.deeps;
                break;
            }
            BuNode temp[]=new BuNode[26];
            for (int j = 0; j <begin.length() ; j++) {
                for (int i = 0; i <26 ; i++) {
                    temp[i]=new BuNode();
                    StringBuffer stringBuffer=new StringBuffer(buNode1.s.toString());
                    temp[i].s=stringBuffer;
                    temp[i].s.replace(j,j+1,word[i]);
                    temp[i].deeps=buNode1.deeps+1;
                    if (list.contains(temp[i].s.toString())){ //分支限界
                        System.out.println(temp[i].s);
                        //list.add(temp[i].s);
                        queue.add(temp[i]);
                        list.remove(temp[i].s.toString());
                    }
                }
            }
        }
        return deeps;
    }
}