A1121

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 (≤ 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 (≤ 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

#include<bits/stdc++.h>
using namespace std;
int N,M,id;
int couple[100005],party[100005],num[100005];
vector<int>ans;
int main(){
    cin>>N;
    couple[0]=-1;
    for(int i=0;i<N;i++){
        int a,b;
        scanf("%d %d",&a,&b);
        couple[a]=b;
        couple[b]=a;
    }
    cin>>M;
    for(int i=0;i<M;i++){
        scanf("%d",&num[i]);
        party[num[i]]=1;
    }
    for(int i=0;i<M;i++){
        if(party[couple[num[i]]]!=1)
            ans.push_back(num[i]);
    }
    sort(ans.begin(),ans.end());
    cout<<ans.size()<<endl;
    for(int i=0;i<ans.size();i++){
        if(i)   printf(" ");
        printf("%05d",ans[i]);
    }
    return 0;
}