[leetcode-332]Reconstruct Itinerary(java)

public class Solution {
HashMap<String,List<String>> maps;
int count;
public List<String> findItinerary(String[][] tickets) {
maps = new HashMap<>();
initHashMap(tickets);

count = tickets.length+1;
List<String> res = new LinkedList<>();
res.add("JFK");
dfs(res);
return res;
}
private boolean dfs(List<String> res){
if(res.size() == count)
return true;
String top = res.get(res.size()-1);
List<String> lists = maps.get(top);
if(lists == null)
return false;

for(int i = 0;i<lists.size();i++){
String tmp = lists.get(i);
res.add(tmp);
lists.remove(i);

if(dfs(res))//当找到合适点之后，直接返回true
return true;
lists.add(i,tmp);//恢复现场
res.remove(res.size()-1);
}
return false;
}
private void initHashMap(String[][] tickets){
for(String[] tmp:tickets){
String from = tmp[0];
String to = tmp[1];

if(!maps.containsKey(from)){
maps.put(from,new LinkedList<>());
}
List<String> list = maps.get(from);

int index = 0;
int size = list.size();
while(index < size){
String cur = list.get(index);
if(cur.compareTo(to) >= 0){
break;
}
index++;
}
list.add(index,to);
}
}
}