#define REP(i,n) for(int i=0;i<(n);++i)
#define FOR(i,a,b) for(int i=(a);i<=(b);++i)
#define RFOR(i,a,b) for(int i=(a);i>=(b);--i)
#define FOREACH(it,c) for(typeof((c).begin())it=(c).begin();it!=(c).end();++it)
#define CLR(x) memset((x),0,sizeof((x)))
#define MP make_pair
#define MPI make_pair
#define PB push_back
typedef long long LL;
typedef vector VI;
typedef vector VS;
typedef pair PI;
class Solution {
public:
int ladderLength(string start, string end, unordered_set &dict) {
if (start == end) return 0;
dict.erase(start);
int len = start.length();
deque > que;
que.push_back(make_pair(start, 1));
while (!que.empty()) {
pair item = que.front();
que.pop_front();
string s = item.first;
int c = item.second;
REP(i,len) {
char bak = s[i];
for (char ch = 'a'; ch <= 'z'; ++ch) {
s[i] = ch;
if (s == end) return c + 1;
if (dict.find(s) != dict.end()) {
que.push_back(make_pair(s, c + 1));
dict.erase(s);
}
}
s[i] = bak;
}
}
return 0;
}
};