1121 Damn Single (25 分)

"Damn Single (单身狗)" is the Chinese nickname for someone who is being single. You are supposed to find those who are alone in a big party, so they can be taken care of.

Input Specification:

Each input file contains one test case. For each case, the first line gives a positive integer N ( $\leq 50,000), the total number of couples. Then N lines of the couples follow, each gives a couple of ID's which are 5-digit numbers (i.e. from 00000 to 99999). After the list of couples, there is a positive integer M (\leq 10,000) followed by M ID's of the party guests. The numbers are separated by spaces. It is guaranteed that nobody is having bigamous marriage (重婚) or dangling with more than one companion.$

Output Specification:

First print in a line the total number of lonely guests. Then in the next line, print their ID's in increasing order. The numbers must be separated by exactly 1 space, and there must be no extra space at the end of the line.

Sample Input:

3
11111 22222
33333 44444
55555 66666
7
55555 44444 10000 88888 22222 11111 23333

Sample Output:

5
10000 23333 44444 55555 88888

注意00000的情况，我wa了一次就是因为这个。

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 int n,m;
 4 map<string,string> mp;
 5 string an[100000];
 6 map<string, int> vis;
 7 vector<string> v;
 8 int main(){
 9     cin >> n;
10     string x,y;
11     for(int i = 0 ; i  < n; i++){
12         cin >> x >> y;
13         mp[x] = y;
14         mp[y] = x;
15     }
16     cin >> m;
17     for(int i = 0 ; i < m; i++){
18         cin >> an[i];
19         vis[an[i]] = 1;
20     }
21     for(int i = 0; i < m; i++){
22         string ans = mp[an[i]];
23         if(vis[ans] != 1){
24             v.push_back(an[i]);
25         }
26     }
27     sort(v.begin(), v.end());
28     cout << v.size()<<endl;
29     for(int i = 0 ; i < v.size(); i++){
30         printf("%s%c", v[i].c_str(), i == v.size()-1?'\n':' ');
31     }
32     return 0;
33 }