Leetcode: Word Ladder

Given two words (start and end), and a dictionary, find the length of shortest transformation sequence from start to end, such that:
Only one letter can be changed at a time
Each intermediate word must exist in the dictionary

For example,

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

As one shortest transformation is "hit" -> "hot" -> "dot" -> "dog" -> "cog",
return its length 5.

Note:

• Return 0 if there is no such transformation sequence.
• All words have the same length.
• All words contain only lowercase alphabetic characters.

BFS: 

int ladderLength(string start, string end, unordered_set &dict) {
        // IMPORTANT: Please reset any member data you declared, as
        // the same Solution instance will be reused for each test case.
		if(start.size() != end.size()) return 0;
		if(start.empty() || end.empty())return 0;
		
		queue path;
		path.push(start);
		int level = 1;
		int count = 1;
		dict.erase(start);
		while(dict.size() > 0 && !path.empty())
		{
			string curword = path.front();
			path.pop();count--;
			for(int i = 0; i < curword.size(); i++)
			{
				string tmp = curword;
				for(char j='a'; j<='z'; j++)
				{
					if(tmp[i]==j)continue;
					tmp[i] = j;
					if(tmp==end)return level+1;
					if(dict.find(tmp) != dict.end()) path.push(tmp);
					dict.erase(tmp);
				}
			}
			if(count==0)
			{
				count = path.size();
				level++;
			}
		}
		return 0;
    }