leetcode_c++:图：Reconstruct Itinerary (332)

class Solution {
public:
vector<string> findItinerary(vector<pair<string, string> > tickets) {
vector<string> res;
unordered_map<string, multiset<string> > m;
for (auto a : tickets) {
m[a.first].insert(a.second);
}
dfs(m, "JFK", res);
return vector<string> (res.rbegin(), res.rend());
}
void dfs(unordered_map<string, multiset<string> > &m, string s, vector<string> &res) {
while (m[s].size()) {
string t = *m[s].begin();
m[s].erase(m[s].begin());
dfs(m, t, res);
}
res.push_back(s);
}
};