vector<vector<string> > sols;

deque<string> oneSol;

public:

vector<vector<string>> findLadders(string start, string end, unordered_set<string> &dict) {

// Start typing your C/C++ solution below

// DO NOT write int main() function

unordered_map<string, list<string> > DirectedGraph;

unordered_map<string, int> pathLen;

//Use BFS to construct a graph

queue<string> q;

queue<int> len;

q.push(start); len.push(1);

pathLen[start] = 1;

typedef unordered_map<string,int>::iterator umit;

while(!q.empty()) {

string curStr = q.front(); int curLen = len.front();

if(curStr == end) break;

q.pop(), len.pop();

for(int i = 0; i < curStr.size(); ++i) {

string temp = curStr;

for(int j = 'a'; j <= 'z'; ++j) {

if(j == curStr[i]) continue;

temp[i] = j;

if(dict.find(temp) != dict.end()) {

umit it = pathLen.find(temp);

if(it == pathLen.end()) {

q.push(temp); len.push(curLen + 1);

pathLen[temp] = curLen + 1;

DirectedGraph[temp].push_back(curStr);

}

else if(it->second == curLen + 1) {

DirectedGraph[temp].push_back(curStr);

}

}

}

}

}

sols.clear(); oneSol.clear();

umit it = pathLen.find(end);

if(it == pathLen.end()) return sols;

GetAllPath(end, start, DirectedGraph);

return sols;

}

void GetAllPath(string& start, string& end, unordered_map<string, list<string> >& DirGraph) {

if(start == end) {

oneSol.push_front(end);

sols.push_back(vector<string>());

copy(oneSol.begin(), oneSol.end(), back_inserter(sols.back()));

oneSol.pop_front();

return;

}

unordered_map<string, list<string> >::iterator it = DirGraph.find(start);

oneSol.push_front(start);

for(list<string>::iterator lit = it->second.begin(); lit != it->second.end(); ++lit)

GetAllPath(*lit, end, DirGraph);

oneSol.pop_front();

}