UVa 10763 - Foreign Exchange

#include<iostream>
#include<cstring>
#include<cstdlib>
#include<cstdio>
#include<cmath>
#include<string>
using namespace std;
int n_cmp(const void *a,const void *b)
{
    return *(int*)a-*(int*)b;
}
int a[500000+2],b[500000+2];
int main()
{
#ifdef test
    freopen("sample.txt","r",stdin);
#endif
    int num;
    while(scanf("%d",&num)!=EOF)
    {
        if(!num)
            break;
        for(int i=0; i<num; i++)
            scanf("%d %d",&a[i],&b[i]);
        qsort(a,num,sizeof(a[0]),n_cmp);
        qsort(b,num,sizeof(b[0]),n_cmp);
        int flag=0;
        for(int i=0; i<num; i++)
            if(a[i]!=b[i])
            {
                flag=1;
                break;
            }
        if(flag==0)
            cout<<"YES"<<endl;
        else
            cout<<"NO"<<endl;
    }
    return 0;
}