Sicily 1021 Couples(数据结构——栈)

//利用堆栈和MAP的映射关系
#include<iostream>
using namespace std;
#include<stack>
#include<map>
int main()
{
int n;
while(cin>>n&&n)
{
map<int,int> m;
stack<int> c;
int m1,m2;
for(int i=0;i<n;i++)
{
cin>>m1>>m2;
m[m1]=m2;
m[m2]=m1;
}
int k;
for( k=1;k<=2*n;k++){
if(!c.empty()&&m[k]!=c.top())
c.push(k);
else if(!c.empty()&&m[k]==c.top())
c.pop();
else c.push(k);
}
if(c.empty())cout<<"Yes"<<endl;
else cout<<"No"<<endl;
}
return 0;
}