Poj 1556 The Doors 计算几何+最短路

#include <cstdio>
#include <cstring>
#include <cmath>
#include <algorithm>
#include <climits>
#include <string>
#include <iostream>
#include <map>
#include <cstdlib>
#include <list>
#include <set>
#include <queue>
#include <stack>
#include <sstream>

using namespace std;

typedef long long LL;
const int maxn = 2000;
const int maxm = 2000 * 2000;
const double INF = 1e30;
const double eps = 1e-7;
struct Point {
double x,y;
Point(double x = 0,double y = 0):x(x),y(y) {}
};

Point str(0,5),end(10,5);
vector<Point> p,pw;
double dist[maxn][maxn],d[maxn];
int N,M;

int dcmp(double x) {
if(fabs(x) < eps) return 0;
if(x < 0) return -1;
return 1;
}

Point operator - (Point a,Point b) {
return Point(a.x - b.x,a.y - b.y);
}

double Cross(Point a,Point b) {
return a.x * b.y - a.y * b.x;
}

double Dot(Point a,Point b) {
return a.x * b.x + a.y * b.y;
}

bool SegmentCross(Point a1,Point a2,Point b1,Point b2) {
double c1 = Cross(a2 - a1,b1 - a1),
c2 = Cross(a2 - a1,b2 - a1),
c3 = Cross(b2 - b1,a1 - b1),
c4 = Cross(b2 - b1,a2 - b1);
return dcmp(c1) * dcmp(c2) < 0 && dcmp(c3) * dcmp(c4) < 0;
}

bool nonecross(Point a1,Point a2) {
for(int i = 0;i < pw.size();i += 2) {
if(SegmentCross(a1,a2,pw[i],pw[i + 1]))
return false;
}
return true;
}

void solve() {
//构建邻接矩阵
M = p.size();
for(int i = 0;i < M;i++) {
for(int j = i + 1;j < M;j++) {
if(nonecross(p[i],p[j])) {
dist[i][j] = dist[j][i] =
sqrt(Dot(p[i]-p[j],p[i]-p[j]));
} else dist[i][j] = INF;
}
}
//bellman-ford
for(int i = 0;i < M;i++) d[i] = INF;
d[0] = 0;
for(int i = 0;i < M;i++) {
for(int j = 0;j < M;j++) {
for(int k = 0;k < M;k++) if(dist[j][k] < INF) {
if(d[j] < INF) {
d[k] = min(d[k],d[j] + dist[j][k]);
}
}
}
}
printf("%.2f\n",d[M - 1]);
}

int main() {
while(cin >> N,N != -1) {
p.clear();
pw.clear();
p.push_back(Point(0,5));
for(int i = 1;i <= N;i++) {
double posx,posy;
cin >> posx;
pw.push_back(Point(posx,0));
for(int j = 0;j < 4;j++) {
cin  >> posy;
p.push_back(Point(posx,posy));
pw.push_back(Point(posx,posy));
}
pw.push_back(Point(posx,10));
}
p.push_back(Point(10,5));
solve();
}
return 0;
}