叉积+二分
通过叉积来判断点在线段的某侧,找到在点右侧的最左边的边,即可判断点在第几个格子内,可以通过二分来优化查询速度
#include <iostream> #include <algorithm> #include <cstdio> using namespace std; const int maxn=1000+10; int n,m,x1,y1,x2,y2; struct segment { int loc1,loc2; }; segment s[maxn]; int c[maxn],res[maxn]; bool cmp(segment a,segment b) { return a.loc1<b.loc1; } int cross(segment ts,int x,int y) { int vx1=ts.loc1-ts.loc2,vy1=y1-y2,vx2=x-ts.loc1,vy2=y-y1; return vx1*vy2-vy1*vx2; } int main() { while(scanf("%d",&n)&&n) { scanf("%d%d%d%d%d",&m,&x1,&y1,&x2,&y2); int i; for(i=1;i<=n;i++) scanf("%d%d",&s[i].loc1,&s[i].loc2); s[0].loc1=x1;s[0].loc2=x1; s[n+1].loc1=x2;s[n+1].loc2=x2; sort(s,s+n+2,cmp); int x,y; memset(c,0,sizeof(c)); memset(res,0,sizeof(res)); for(i=0;i<m;i++) { scanf("%d%d",&x,&y); int high=n+2,low=0,mid; while(low<high)//找到在点右侧的最左边的边,即可判断点在第几个格子内 { mid=low+(high-low)/2; if(cross(s[mid],x,y)>0) high=mid; else low=mid+1; } c[low]++; } for(i=1;i<=n+1;i++) res[c[i]]++; printf("Box\n"); for(i=1;i<=n+1;i++) if(res[i]) printf("%d: %d\n",i,res[i]); } return 0; }