几何+思维——cf1299b

结论：只要多边形的所有对边都是两两平行的，就一定能满足条件

#include<bits/stdc++.h>
using namespace std;
#define N 300006
#define ll long long 

ll n,x[N],y[N];

int main(){
    cin>>n;
    for(int i=0;i<n;i++)cin>>x[i]>>y[i];
    if(n%2){puts("nO");return 0;}
    for(int i=0;i<n/2;i++){
        ll x1=x[i]-x[i+1],y1=y[i]-y[i+1];
        ll x2=x[i+n/2]-x[(i+n/2+1)%n];
        ll y2=y[i+n/2]-y[(i+n/2+1)%n]; 
        if(x1!=-x2 || y1!=-y2){puts("nO");return 0;}
    }
    puts("YES");
}