1 //bfs
2 class Solution {
3 public:
4 typedef unordered_map<string, int> MyHashMap;
5 int ladderLength(string start, string end, unordered_set<string> &dict) {
6 if (start == end)
7 return 1;
8 if (start.length() != end.length())
9 return 0;
10 queue<string> qs;
11 int len = start.length();
12 qs.push(start);
13 MyHashMap mp;
14 mp[start] = 1;
15 while (!qs.empty()){
16 string cur = qs.front();
17 qs.pop();
18 for (int i = 0; i < len; i++){
19 for (int j = 0; j < 26; j++){
20 string tmp = cur;
21 tmp[i] = 'a'+j;
22 if (tmp == end)
23 return mp[cur]+1;
24 if (dict.find(tmp) == dict.end())
25 continue;
26 if (mp.find(tmp) != mp.end())
27 continue;
28 qs.push(tmp);
29 mp[tmp] = mp[cur] + 1;
30 }
31 }
32 }
33 return 0;
34 }
35 };
