53 lines
1.3 KiB
C++
53 lines
1.3 KiB
C++
#include<iostream>
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using namespace std;
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#define N 40005
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struct node{
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double x,y;
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}p[N];
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int n;
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double cal_dis(int x,int y){
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double x1=p[x].x,y1=p[x].y;
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double x2=p[y].x,y2=p[y].y;
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return (x1-x2)*(x1-x2)+(y1-y2)*(y1-y2);
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}
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int main(void){
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while(~scanf("%d",&n)){
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int k=1;
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for(int i=1;i<=n;i++){
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scanf("%lf%lf",&p[k].x,&p[k].y);
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if(k!=1&&k%2){
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p[k-1].x=(p[k-2].x+p[k].x)/2.0;
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p[k-1].y=(p[k-2].y+p[k].y)/2.0;
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}
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k+=2;
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}
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p[k-1].x=(p[1].x+p[k-2].x)/2.0;
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p[k-1].y=(p[1].y+p[k-2].y)/2.0;
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bool flag=0;
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for(int i=1;i<=n;i++){
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double x1=p[i].x-p[i+n].x;
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double y1=p[i].y-p[i+n].y;
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int j,k;
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k=i-1;
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j=i+1;
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for(;j<=i+n;j++,k--){
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if(k<=0) k=2*n;
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double x2=p[j].x-p[k].x;
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double y2=p[j].y-p[k].y;
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if(x1*x2+y1*y2!=0)
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break;
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if(cal_dis(i,j)!=cal_dis(i,k))
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break;
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}
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if(j>i+n){
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flag=1;
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break;
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}
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}
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if(flag)
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printf("YES\n");
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else
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printf("NO\n");
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}
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}
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