Word Ladder

Word Ladder

Given two words (beginWord and endWord), and a dictionary, find the length of shortest transformation sequence from beginWord to endWord, 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"]

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.

class Solution {public:    int ladderLength(string start, string end, unordered_set<string> &dict) {        if(start.size() != end.size()) return 0;        if(start.empty() || end.empty()) return 0;                queue<string> 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;    }};