Submission #132391

#	Time	Username	Problem	Language	Result	Execution time	Memory
132391		duality	Fences (JOI18_fences)	C++11	0 / 100	2 ms	376 KiB

fences

#include <bits/stdc++.h>
using namespace std;
#define mp make_pair
#define pb push_back
typedef long long int LLI;
typedef vector<int> vi;
typedef pair<int,int> pii;
typedef vector<pii> vpii;
#define x first
#define y second
#define point pair<double,double>
#define EPS 1e-9

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);
}
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;
}
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 closest(p,s) == p;
}
int inter(point a,point b,point c,point d) {
    if (comp(a,c) || comp(a,d) || comp(b,c) || comp(b,d)) return 0;
    else return (ccw(a,b,d) != ccw(a,b,c)) && (ccw(c,d,a) != ccw(c,d,b));
}
point points[200];
double dist[400][400];
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;
    if ((a.x+b.x > -2*S+EPS) && (a.x+b.x < 2*S-EPS) && (a.y+b.y > -2*S+EPS) && (a.y+b.y < 2*S-EPS)) 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;
}
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,k,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);
    c = unique(points,points+c,comp)-points;
    for (i = 0; i < 2*c; i++) fill(dist[i],dist[i]+2*c,1e99),dist[i][i] = 0;
    for (i = 0; i < c; i++) {
        for (j = i+1; j < c; j++) {
            point a = points[i],b = points[j];
            for (k = 0; k < N; k++) {
                if (onSeg(a,s[k]) && onSeg(b,s[k])) break;
            }
            if (check(a,b,S)) {
                double d = (k < N) ? 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(1e5,1))) {
                    dist[2*i][2*j+1] = dist[2*i+1][2*j] = d;
                    dist[2*j][2*i+1] = dist[2*j+1][2*i] = d;
                }
                else {
                    dist[2*i][2*j] = dist[2*i+1][2*j+1] = d;
                    dist[2*j][2*i] = dist[2*j+1][2*i+1] = d;
                }
            }
        }
    }
    for (k = 0; k < 2*c; k++) {
        for (i = 0; i < 2*c; i++) {
            for (j = 0; j < 2*c; j++) dist[i][j] = min(dist[i][j],dist[i][k]+dist[k][j]);
        }
    }
    double ans = 1e99;
    for (i = 0; i < c; i++) ans = min(ans,dist[2*i][2*i+1]);
    printf("%.10lf\n",ans);

    return 0;
}

Compilation message (stderr)

fences.cpp: In function 'int main()':
fences.cpp:53:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d %d",&N,&S);
     ~~~~~^~~~~~~~~~~~~~~
fences.cpp:54:34: 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);
                             ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 18
• Subtask 2: 0 / 33
• Subtask 3: 0 / 49