题意：给你两条线段，求所能接的雨水的面积
#include <iostream> #include <cstring> #include <string> #include <cmath> #include <algorithm> #include <cstdio> using namespace std; #define eps 1e-8 int sig(double x) { if(x<-eps)return -1; if(x>eps)return 1; return 0; } struct point { double x,y; }; point operator-(point a,point b) { point ret; ret.x=a.x-b.x; ret.y=a.y-b.y; return ret; } struct line { point p,q; } L1,L2; // 点o在直线L上 int inside(point o,line L) { double xl=min(L.p.x,L.q.x); double xr=max(L.p.x,L.q.x); double yl=min(L.p.y,L.q.y); double yr=max(L.p.y,L.q.y); if(sig(o.x-xl)>=0&&sig(xr-o.x)>=0&&sig(o.y-yl)>=0&&sig(yr-o.y)>=0) return 1; else return 0; } //交点 point Intersect(line u,line v) { point ret=u.p; double t=((u.p.x-v.p.x)*(v.p.y-v.q.y)-(u.p.y-v.p.y)*(v.p.x-v.q.x))/((u.p.x-u.q.x)*(v.p.y-v.q.y)-(u.p.y-u.q.y)*(v.p.x-v.q.x)); ret.x+=(u.q.x-u.p.x)*t; ret.y+=(u.q.y-u.p.y)*t; return ret; } // 计算三角形面积 double coun(point a,point b,point o) { double ans; a=a-o; b=b-o; if(sig(a.x*b.y-a.y*b.x)==0)return 0; if(a.y<eps||b.y<eps)return 0; point tem; if(a.y<b.y) { tem=a; a=b; b=tem; } if(sig(a.x)==0) ans=fabs(b.x*b.y)*0.5; else { double k=a.y/a.x; double x=b.y/k; if(sig((x-b.x)*(a.x-b.x))<=0) ans=0; else ans=fabs(b.x-x)*b.y*0.5; } return ans; } double solve() { double ans; point o; o=Intersect(L1,L2); if(inside(o,L1)&&inside(o,L2)) { ans=coun(L1.p,L2.p,o); ans=max(ans,coun(L1.p,L2.q,o)); ans=max(ans,coun(L1.q,L2.p,o)); ans=max(ans,coun(L1.q,L2.q,o)); return ans; } return 0; } int main() { int i,j,tt; double ans; while(scanf("%d",&tt)!=EOF) { while(tt--) { scanf("%lf%lf%lf%lf",&L1.p.x,&L1.p.y,&L1.q.x,&L1.q.y); scanf("%lf%lf%lf%lf",&L2.p.x,&L2.p.y,&L2.q.x,&L2.q.y); printf("%.2f ",solve()); } } }