Submission #81816

#TimeUsernameProblemLanguageResultExecution timeMemory
81816tmwilliamlin168Fences (JOI18_fences)C++14
18 / 100
3 ms836 KiB
#include <bits/stdc++.h> using namespace std; const int mxN=100, mxM=2*mxN+4, MG1=1000696969; int n, s, a[mxM], b[mxM], m; double d[2*mxM][2*mxM], ans=6969; int main() { ios_base::sync_with_stdio(0); cin.tie(0); cin >> n >> s; for(int i=0; i<n; ++i) cin >> a[2*i] >> b[2*i] >> a[2*i+1] >> b[2*i+1]; a[2*n]=a[2*n+1]=b[2*n]=b[2*n+3]=s; a[2*n+2]=a[2*n+3]=b[2*n+1]=b[2*n+2]=-s; m=2*n+4; for(int i=0; i<2*m; ++i) for(int j=0; j<2*m; ++j) d[i][j]=8*s; auto o1=[&](long long x1, long long y1, int x2, int y2) { return x1*y2==x2*y1?0:(x1*y2>x2*y1?1:-1); }; auto il=[&](int x1, int y1, int x2, int y2, int x3, int y3, int x4, int y4) { return o1(x2-x1, y2-y1, x3-x1, y3-y1)==-o1(x2-x1, y2-y1, x4-x1, y4-y1)&&o1(x4-x3, y4-y3, x1-x3, y1-y3)==-o1(x4-x3, y4-y3, x2-x3, y2-y3); }; auto gc=[&](int x1, int y1, int x2, int y2) { return il(x1, y1, x2, y2, 0, 0, MG1, 1)?o1(x1, y1, MG1, 1):0; }; auto aa=[&](int u, int v, double e, int c) { if(c>=0) { d[u][v+c*m]=min(e, d[u][v+c*m]); d[v+c*m][u]=min(e, d[v+c*m][u]); } if(c<=0) { d[u+m][v+(1+c)*m]=min(e, d[u+m][v+(1+c)*m]); d[v+(1+c)*m][u+m]=min(e, d[v+(1+c)*m][u+m]); } }; for(int i=0; i<n; ++i) for(int j=i+1; j<n; ++j) if(il(a[2*i], b[2*i], a[2*i+1], b[2*i+1], a[2*i+2], b[2*i+2], a[2*i+3], b[2*i+3])) for(int k=0; k<4; ++k) aa(2*i+k%2, 2*j+k/2, 0, gc(a[2*i+k%2], b[2*i+k%2], a[2*j+k/2], b[2*j+k/2])); auto is=[&](long long x1, long long y1, int x2, int y2, int s, double &d) { for(int i=2*n; i<2*n+2; ++i) if(il(x1, y1, x2, y2, a[i]*s, b[i]*s, a[i+2]*s, b[i+2]*s)) return; d=sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2))/s; }; for(int i=0; i<m; ++i) { for(int j=0; j<n+2; ++j) { double d1=8*s; for(int k=2*j; k<2*j+2; ++k, d1=8*s) { is(a[i], b[i], a[k], b[k], 1, d1); if(d1<8*s) aa(i, k, d1, gc(a[i], b[i], a[k], b[k])); } if(j<n) { int bx=a[2*j+1]-a[2*j], by=b[2*j+1]-b[2*j], bm=bx*bx+by*by, adb=(a[i]-a[2*j])*bx+(b[i]-b[2*j])*by; if(0<=adb&&adb<=bm) { int cx=adb*bx+a[2*j]*bm, cy=adb*by+b[2*j]*bm; if(a[i]==-80&&b[i]==80&&a[2*j]==-92) cout << bm << " " << cx << " " << cy << endl; is(a[i]*bm, b[i]*bm, cx, cy, bm, d1); if(d1<8*s) for(int k=2*j; k<2*j+2; ++k) aa(i, k, d1, gc(a[i]*bm, b[i]*bm, cx, cy)+gc(cx, cy, a[k]*bm, b[k]*bm)); } } } } for(int k=0; k<2*m; ++k) for(int i=0; i<2*m; ++i) for(int j=0; j<2*m; ++j) d[i][j]=min(d[i][k]+d[k][j], d[i][j]); for(int i=0; i<m; ++i) ans=min(d[i][i+m], ans); cout << fixed << setprecision(9) << ans; }
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