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QOJ
ID | Problem | Submitter | Result | Time | Memory | Language | File size | Submit time | Judge time |
---|---|---|---|---|---|---|---|---|---|
#313840 | #7730. Convex Checker | Hqwq | WA | 1ms | 7808kb | C++14 | 1.7kb | 2024-01-25 00:36:43 | 2024-01-25 00:36:43 |
Judging History
answer
#include<bits/stdc++.h>
using namespace std;
int n,cnt;
struct point{
int x,y;
}p[200010],v[200010],q[200010];
bool cmp(point x,point y){
if (x.x!=y.x) return x.x<y.x;
return x.y<y.y;
}
bool check(point x,point y,point z){
point l1,l2;
l1.x=y.x-x.x;
l1.y=y.y-x.y;
l2.x=z.x-y.x;
l2.y=z.y-y.y;
if (l1.x*l2.y-l2.x*l1.y>0) return 1;
return 0;
}
void tb(){
point p1,p2;
v[++cnt]=p[1];
v[++cnt]=p[2];
for (int i=3;i<=n;i++){
p1=v[cnt-1];
p2=v[cnt];
while(!check(p1,p2,p[i]) && cnt>1){
cnt--;
p1=v[cnt-1];
p2=v[cnt];
}
v[++cnt]=p[i];
}
int temp=cnt;
v[++cnt]=p[n-1];
for (int i=n-2;i>=1;i--){
p1=v[cnt-1];
p2=v[cnt];
while(!check(p1,p2,p[i]) && cnt>temp){
cnt--;
p1=v[cnt-1];
p2=v[cnt];
}
v[++cnt]=p[i];
}
cnt--;
}
int main(){
scanf("%d",&n);
int m=0;
for (int i=1;i<=n;i++){
int x,y;
scanf("%d %d",&p[i].x,&p[i].y);
q[i]=p[i];
}
sort(p+1,p+1+n,cmp);
tb();
int pp=1;
if (cnt!=n) pp=0;
else {
int i=1,j;
for (i=1;i<=n;i++) if (q[1].x==v[i].x && q[1].y==v[i].y) break;
int p1=1,p2=1;
j=1;
while(j<=n){
if (v[i].x!=q[j].x || v[i].y!=q[j].y){
p1=0;
break;
}
i=i%n+1;
j=j+1;
}
j=n;
while(j>=1){
if (v[i].x!=q[j].x || v[i].y!=q[j].y){
p2=0;
break;
}
i=(i+n-2)%n+1;
j=j+1;
}
pp=p1|p2;
}
if (pp) printf("Yes\n");
else printf("No\n");
}
Details
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Test #1:
score: 100
Accepted
time: 1ms
memory: 5852kb
input:
3 0 0 1 0 0 1
output:
Yes
result:
ok answer is YES
Test #2:
score: -100
Wrong Answer
time: 0ms
memory: 7808kb
input:
4 0 0 0 1 1 1 1 0
output:
No
result:
wrong answer expected YES, found NO