算法竞赛入门经典(第二版)-刘汝佳-第五章 交流生

#include<cstdio>#include<cstring>#include<cstdlib>#include<string>#include<sstream>#include<iostream>#include<algorithm>#include<set>#include<map>#include<vector>using namespace std;struct node{int a,b;node(int x,int y){a=x,b=y;}bool operator < (const node &n) const{if(n.a!=a)   return n.a<a;return n.b<b;}};int main(){//freopen("1.txt","r",stdin);//freopen("out.txt","w",stdout);int n;while(scanf("%d",&n),n){map<node,int> m;int i,j;for(i=0;i<n;i++){int a,b;scanf("%d%d",&a,&b);node x(a,b);m[x]++;j++;}map<node,int>::iterator it;for(it=m.begin();it!=m.end();it++){node x=it->first;swap(x.a,x.b);if( it->second!=m[x] ) break;}if(it==m.end()) printf("YES\n");else printf("NO\n");}return 0;}

ps

1.结构体所有元素都要排序。