#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <limits.h>
#include <stack>
#include <queue>
#include <map>
#include <set>
#include <algorithm>
#include <string>
#include <functional>
#include <vector>
#include <numeric>
#include <deque>
#include <utility>
#include <bitset>
#include <iostream>
using namespace std;
typedef long long lint;
typedef long double llf;
typedef pair<double, double> pi;
int n;
int x[50005], y[50005];
struct line{
double a, b, c;
}v[50005];
pi rotate(pi a, pi b, double q){
int dx = a.second - b.second;
int dy = b.first - a.first;
double pyth = hypot(dx, dy);
return pi(b.first + (dx / pyth) * q, b.second + (dy / pyth) * q);
}
pi cross(line p, line q){
double base = p.a * q.b - p.b * q.a;
if(fabs(base) < 1e-5) return pi(1e9, 1e9);
return pi((p.b * q.c - q.b * p.c) / base, (p.c * q.a - q.c * p.a) / base);
}
bool ccw(pi a, pi b, pi c){
double dx1 = b.first - a.first;
double dy1 = b.second - a.second;
double dx2 = c.first - a.first;
double dy2 = c.second - a.second;
return dx1 * dy2 > dy1 * dx2;
}
double func(line a, pi b){
return a.a * b.first + a.b * b.second + a.c;
}
bool bad;
bool low(line a, line b, line c){
pi t = cross(a, c);
if(fabs(t.first - 1e9) <= 1e-4){
if(func(a, cross(b, c)) <= 0){
bad = 1;
}
return 0;
}
if(func(c, cross(a, b)) <= 0){
if(func(b, cross(a, c)) <= 0){
bad = 1;
}
return 1;
}
return 0;
}
void get_points(vector<pi> &ret){
bad = 0;
deque<line> dq;
for(int i=0; i<n; i++){
while(dq.size() >= 2 && low(dq[dq.size()-2], dq.back(), v[i])){
dq.pop_back();
}
dq.push_back(v[i]);
}
while(dq.size() >= 3 && low(dq.back(), dq[0], dq[1])){
dq.pop_front();
}
if(bad) return;
if(dq.size() <= 2) return;
for(int i=0; i<dq.size()-1; i++){
ret.push_back(cross(dq[i], dq[i+1]));
}
ret.push_back(cross(dq.back(), dq.front()));
}
bool trial(double d){
for(int i=0; i<n; i++){
int a = y[i] - y[i+1];
int b = x[i+1] - x[i];
pi loc = rotate(pi(x[i], y[i]), pi(x[i+1], y[i+1]), d);
v[i] = {1.0 * a, 1.0 * b, - a * loc.first - b * loc.second}; // ax + by + c >= 0
}
vector<pi> p;
get_points(p);
if(p.empty()) return 0;
swap(p[0], *min_element(p.begin(), p.end()));
sort(p.begin() + 1, p.end(), [&](const pi &a, const pi &b){
return ccw(p[0], a, b);
});
auto dist = [&](pi a, pi b){
return hypot(b.first - a.first, b.second - a.second);
};
int pt = 0;
for(int i=0; i<p.size(); i++){
while(pt+1 < p.size() && dist(p[i], p[pt]) < dist(p[i], p[pt+1])){
pt++;
}
if(dist(p[i], p[pt]) >= 2 * d) return 1;
}
return 0;
}
int main(){
scanf("%d",&n);
for(int i=0; i<n; i++){
scanf("%d %d",&x[i],&y[i]);
}
x[n] = x[0], y[n] = y[0];
double s = 0, e = 1e7;
for(int i=0; i<50; i++){
double m = (s+e)/2;
if(trial(m)) s = m;
else e = m;
}
printf("%.3f",s);
}
Compilation message
2circles.cpp: In function 'void get_points(std::vector<std::pair<double, double> >&)':
2circles.cpp:89:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
for(int i=0; i<dq.size()-1; i++){
^
2circles.cpp: In function 'bool trial(double)':
2circles.cpp:113:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
for(int i=0; i<p.size(); i++){
^
2circles.cpp:114:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
while(pt+1 < p.size() && dist(p[i], p[pt]) < dist(p[i], p[pt+1])){
^
2circles.cpp: In function 'int main()':
2circles.cpp:123:19: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
scanf("%d",&n);
^
2circles.cpp:125:35: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
scanf("%d %d",&x[i],&y[i]);
^
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
0 ms |
3600 KB |
Output is correct |
| 2 |
Correct |
0 ms |
3600 KB |
Output is correct |
| 3 |
Correct |
0 ms |
3600 KB |
Output is correct |
| 4 |
Correct |
0 ms |
3600 KB |
Output is correct |
| 5 |
Correct |
9 ms |
3736 KB |
Output is correct |
| 6 |
Incorrect |
83 ms |
4268 KB |
Output isn't correct |
| 7 |
Incorrect |
69 ms |
4020 KB |
Output isn't correct |
| 8 |
Incorrect |
83 ms |
4364 KB |
Output isn't correct |
| 9 |
Incorrect |
239 ms |
4524 KB |
Output isn't correct |
| 10 |
Incorrect |
229 ms |
6680 KB |
Output isn't correct |
