Word Ladder II

Given two words (start and end), and a dictionary, find all shortest transformation sequence(s) from start to end, such that:

1. Only one letter can be changed at a time
2. Each intermediate word must exist in the dictionary

For example,

Given:
start = "hit"
end = "cog"
dict = ["hot","dot","dog","lot","log"]

Return

  [
    ["hit","hot","dot","dog","cog"],
    ["hit","hot","lot","log","cog"]
  ]

Note:

• All words have the same length.

• All words contain only lowercase alphabetic characters.

  class Solution {
  public:
      vector> findLadders(string start, string end, unordered_set &dict) {
          vector> ret;
  		map level;//每个词都有一个层次，层次要尽可能小
  		map> father;//前驱节点
  		vector temp;
  		father[start]=temp;
  		
  		for(auto i=dict.begin();i!=dict.end();i++)
  		{
  			level[*i]=-1;
  		}
  		level[start]=1;
  		level[end]=-1;
  
  		dict.insert(end);
  		queue q;
  		q.push(start);
  		while(!q.empty())
  		{
  			string cur=q.front();
  			string origi=cur;
  			if(level[end]!=-1 && level[cur]>=level[end])
  				break;
  			q.pop();
  			for(int i=0;i> gen_path(string point,map> &father)
  	{
  		vector> ret;
  		if(father[point].empty())
  		{
  			vector ta;
  			ta.push_back(point);
  			ret.push_back(ta);
  			return ret;
  		}
  		else
  		{
  			for(int i=0;i!=father[point].size();i++)
  			{
  				vector> oth=gen_path(father[point][i],father);
  				for(int j=0;j!=oth.size();j++)
  				{
  					vector temp;
  					temp.push_back(point);
  					temp.insert(temp.end(),oth[j].begin(),oth[j].end());
  					ret.push_back(temp);
  				}
  			}
  			return ret;
  		}
  	}
  };