poj2318——TOYS

题意：求图中各个区域中有多少个玩具。

思路：外积+二分

ps:这小家伙确实淘气 只知当时头挺晕的...撑着将此题过了。休息

#include<iostream> #include<cstring> #include<cstdio> using namespace std; class T { public: int x1,x2; }; T toy[5005]; int g[5005]; int y1,y2,n,m,x,y,t; int f(int x1,int x2) { int f1=(toy[x1].x2-x)*(y1-y)-(y2-y)*(toy[x1].x1-x); int f2=(toy[x2].x2-x)*(y1-y)-(y2-y)*(toy[x2].x1-x); if(f1<0&&f2>0) return 0; else if(f1>0) return -1;//直线左 else return 1;//直线右 } void solve(int left,int right) { int mid=(left+right)/2; int k=f(mid,mid+1); if(k==0) {t=mid;return ;} else if(k<0) solve(left,mid); else solve(mid+1,right); } int main() { while(1) { int i; cin>>n; if(n==0) break; cin>>m>>toy[0].x1>>y1>>toy[n+1].x2>>y2; toy[0].x2=toy[0].x1;toy[n+1].x1=toy[n+1].x2; for(i=1;i<=n;i++) cin>>toy[i].x1>>toy[i].x2; memset(g,0,sizeof(g)); for(i=0;i<m;i++) { cin>>x>>y; solve(0,n+1); g[t]+=1; } for(i=0;i<=n;i++) { printf("%d: %d\n",i,g[i]); } printf("\n"); } return 0; }