10763:Foreign Exchange

Foreign Exchange

version 1(100ms):

#include<cstdio>
#include<map>
#include<set>
using namespace std;
int n;
int main(){
    while(scanf("%d",&n) && n){
        map<int,int>ori,tar;
        set<int>sch;
        int a,b;
        for(int i = 0;i < n;i++){
            scanf("%d %d",&a,&b);
            if(!ori.count(a)) ori[a] = 0;
            if(!tar.count(b)) tar[b] = 0;
            ori[a]++,tar[b]++;
            sch.insert(a);
        }
        int mark = 1;
        for(set<int>::iterator it = sch.begin();it != sch.end() && mark;it++){
            if(!tar.count(*it) || tar[*it] != ori[*it]) mark = 0;
        }
        printf("%s\n",mark ? "YES" : "NO");
    }
    return 0;
}