This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
#define DEBUG 0
#include <bits/stdc++.h>
using namespace std;
#if DEBUG
// basic debugging macros
int __i__,__j__;
#define printLine(l) for(__i__=0;__i__<l;__i__++){cout<<"-";}cout<<endl
#define printLine2(l,c) for(__i__=0;__i__<l;__i__++){cout<<c;}cout<<endl
#define printVar(n) cout<<#n<<": "<<n<<endl
#define printArr(a,l) cout<<#a<<": ";for(__i__=0;__i__<l;__i__++){cout<<a[__i__]<<" ";}cout<<endl
#define print2dArr(a,r,c) cout<<#a<<":\n";for(__i__=0;__i__<r;__i__++){for(__j__=0;__j__<c;__j__++){cout<<a[__i__][__j__]<<" ";}cout<<endl;}
#define print2dArr2(a,r,c,l) cout<<#a<<":\n";for(__i__=0;__i__<r;__i__++){for(__j__=0;__j__<c;__j__++){cout<<setw(l)<<setfill(' ')<<a[__i__][__j__]<<" ";}cout<<endl;}
// advanced debugging class
// debug 1,2,'A',"test";
class _Debug {
public:
template<typename T>
_Debug& operator,(T val) {
cout << val << endl;
return *this;
}
};
#define debug _Debug(),
#else
#define printLine(l)
#define printLine2(l,c)
#define printVar(n)
#define printArr(a,l)
#define print2dArr(a,r,c)
#define print2dArr2(a,r,c,l)
#define debug
#endif
// define
#define MAX_VAL 999999999
#define MAX_VAL_2 999999999999999999LL
#define EPS 1e-9
#define mp make_pair
#define pb push_back
// typedef
typedef unsigned int UI;
typedef long long int LLI;
typedef unsigned long long int ULLI;
typedef unsigned short int US;
typedef pair<int,int> pii;
typedef pair<LLI,LLI> plli;
typedef vector<int> vi;
typedef vector<LLI> vlli;
typedef vector<pii> vpii;
typedef vector<plli> vplli;
// ---------- END OF TEMPLATE ----------
#define x first
#define y second
#define point pair<double,double>
struct seg { point a,b; };
seg s[104];
bool comp(point a,point b) {
return (abs(a.x-b.x) < EPS) && (abs(a.y-b.y) < EPS);
}
bool comp2(point a,point b) {
if (abs(a.x-b.x) < EPS) return a.y < b.y-EPS;
else return a.x < b.x;
}
int ccw(point a,point b,point c) {
return (b.x-a.x)*(c.y-a.y) > (b.y-a.y)*(c.x-a.x)+EPS;
}
int coll(point a,point b,point c) {
return abs((b.x-a.x)*(c.y-a.y)-(b.y-a.y)*(c.x-a.x)) < EPS;
}
point closest(point p,seg s) {
if (s.a == s.b) return s.a;
point a = s.a,b = s.b;
point ap = mp(p.x-a.x,p.y-a.y),ab = mp(b.x-a.x,b.y-a.y);
double f = (ap.x*ab.x+ap.y*ab.y)/(ab.x*ab.x+ab.y*ab.y);
if (f < 0) return a;
if (f > 1) return b;
return mp((1-f)*a.x+f*b.x,(1-f)*a.y+f*b.y);
}
int onSeg(point p,seg s) {
return comp(closest(p,s),p);
}
int inter(point a,point b,point c,point d) {
if (coll(a,b,c) || coll(a,b,d) || coll(c,d,a) || coll(c,d,b)) return 0;
else return (ccw(a,b,d) != ccw(a,b,c)) && (ccw(c,d,a) != ccw(c,d,b));
}
point points[22000];
int check(point a,point b,int S) {
if ((a.x > -S+EPS) && (a.x < S-EPS) && (a.y > -S+EPS) && (a.y < S-EPS)) return 0;
if ((b.x > -S+EPS) && (b.x < S-EPS) && (b.y > -S+EPS) && (b.y < S-EPS)) return 0;
point c = (point){(1-1e-6)*a.x+1e-6*b.x,(1-1e-6)*a.y+1e-6*b.y};
if ((c.x > -S+EPS) && (c.x < S-EPS) && (c.y > -S+EPS) && (c.y < S-EPS)) return 0;
c = (point){(1-1e-6)*b.x+1e-6*a.x,(1-1e-6)*b.y+1e-6*a.y};
if ((c.x > -S+EPS) && (c.x < S-EPS) && (c.y > -S+EPS) && (c.y < S-EPS)) return 0;
if (onSeg(mp(0,0),(seg){a,b})) return 0;
if (inter(a,b,mp(S,S),mp(S,-S))) return 0;
if (inter(a,b,mp(S,-S),mp(-S,-S))) return 0;
if (inter(a,b,mp(-S,-S),mp(-S,S))) return 0;
if (inter(a,b,mp(-S,S),mp(S,S))) return 0;
return 1;
}
vector<pair<int,double> > adjList[44000];
int addEdge(point a,point b,int N,int c,int S,int f) {
int u = lower_bound(points,points+c,a,comp2)-points;
int v = lower_bound(points,points+c,b,comp2)-points;
if (check(a,b,S)) {
double d = f ? 0:sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));
if (inter(a,b,mp(0,0),mp(1e9,1))) {
adjList[2*u].pb(mp(2*v+1,d)),adjList[2*u+1].pb(mp(2*v,d));
adjList[2*v].pb(mp(2*u+1,d)),adjList[2*v+1].pb(mp(2*u,d));
}
else {
adjList[2*u].pb(mp(2*v,d)),adjList[2*u+1].pb(mp(2*v+1,d));
adjList[2*v].pb(mp(2*u,d)),adjList[2*v+1].pb(mp(2*u+1,d));
}
}
return 0;
}
double dist[44000];
priority_queue<pair<double,int> > H;
double findDist(int s,int c) {
int i;
for (i = 0; i < 2*c; i++) dist[i] = 1e99;
dist[2*s] = 0,H.push(mp(0,2*s));
while (!H.empty()) {
int u = H.top().second;
double d = -H.top().first;
H.pop();
if (d > dist[u]) continue;
for (i = 0; i < adjList[u].size(); i++) {
int v = adjList[u][i].first;
if (d+adjList[u][i].second < dist[v]) {
dist[v] = d+adjList[u][i].second;
H.push(mp(-dist[v],v));
}
}
}
return dist[2*s+1];
}
int main() {
int i;
int N,S;
scanf("%d %d",&N,&S);
for (i = 0; i < N; i++) scanf("%lf %lf %lf %lf",&s[i].a.x,&s[i].a.y,&s[i].b.x,&s[i].b.y);
s[N] = (seg){mp(S,S),mp(S,S)};
s[N+1] = (seg){mp(S,-S),mp(S,-S)};
s[N+2] = (seg){mp(-S,S),mp(-S,S)};
s[N+3] = (seg){mp(-S,-S),mp(-S,-S)};
N += 4;
int j,c = 0;
for (i = 0; i < N; i++) {
for (j = 0; j < N; j++) points[c++] = closest(s[i].a,s[j]),points[c++] = closest(s[i].b,s[j]);
}
sort(points,points+c,comp2);
c = unique(points,points+c,comp)-points;
for (i = 0; i < N; i++) {
for (j = 0; j < N; j++) {
if (i != j) {
addEdge(s[i].a,closest(s[i].a,s[j]),N,c,S,0);
addEdge(s[i].b,closest(s[i].b,s[j]),N,c,S,0);
}
}
}
for (i = 0; i < N; i++) {
for (j = 0; j < c; j++) {
if (onSeg(points[j],s[i])) addEdge(points[j],s[i].a,N,c,S,1);
}
}
double ans = 1e99;
for (i = 0; i < N; i++) {
ans = min(ans,findDist(lower_bound(points,points+c,s[i].a,comp2)-points,c));
ans = min(ans,findDist(lower_bound(points,points+c,s[i].b,comp2)-points,c));
}
printf("%.10lf\n",ans);
return 0;
}
Compilation message (stderr)
fences.cpp: In function 'double findDist(int, int)':
fences.cpp:136:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
for (i = 0; i < adjList[u].size(); i++) {
~~^~~~~~~~~~~~~~~~~~~
fences.cpp: In function 'int main()':
fences.cpp:149:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
scanf("%d %d",&N,&S);
~~~~~^~~~~~~~~~~~~~~
fences.cpp:150:34: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
for (i = 0; i < N; i++) scanf("%lf %lf %lf %lf",&s[i].a.x,&s[i].a.y,&s[i].b.x,&s[i].b.y);
~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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