二分+叉积判断方向 poj 2318 2398

 // 题意：问你每个区域有多少个点
 // 思路：数据小可以直接暴力
 // 也可以二分区间
 
 #include <cstdio>
 #include <cstring>
 #include <iostream>
 #include <algorithm>
 #include <map>
 #include <set>
 #include <queue>
 #include <stdlib.h>
 #include <cmath>
 using namespace std;
 typedef long long LL;
 const LL inf = 1e18;
 const int N = ;
 
 struct Point{
     int x,y;
     Point(){}
     Point(int _x,int _y){
         x=_x;y=_y;
     }
     Point operator -(const Point &b)const{
         return Point(x-b.x,y-b.y);
     }
     int operator *(const Point &b)const{
         return x*b.x+y*b.y;
     }
     int operator ^(const Point &b)const{
         return x*b.y-y*b.x;
     }
 };
 
 struct Line{
     Point s,e;
     Line(){}
     Line(Point _s,Point _e){
         s=_s,e=_e;
     }
 };
 
 int xmult(Point p0,Point p1,Point p2){
     return (p1-p0)^(p2-p0);
 }
 
 Line line[N];
 int ans[N];
 int main(){
     int n,m,x1,y1,x2,y2;
     bool first = true;
     while(~scanf("%d",&n)&&n){
         if(first) first=false;
         else printf("\n");
         scanf("%d%d%d%d%d",&m,&x1,&y1,&x2,&y2);
         for(int i=;i<n;i++){
             int x,y;
             scanf("%d%d",&x,&y);
             line[i]=Line(Point(x,y1),Point(y,y2));
         }
         line[n]=Line(Point(x2,y1),Point(x2,y2));
         int x,y;
         Point p;
         memset(ans,,sizeof(ans));
         int tem;
         while(m--){
             scanf("%d%d",&x,&y);
             p = Point(x,y);
             int l=,r=n,mid;
             while(l<=r){
                 mid=(l+r)>>;
                 if(xmult(p,line[mid].s,line[mid].e)<){
                     tem=mid;
                     r=mid-;
                 }
                 else l=mid+;
             }
             ans[tem]++;
         }
         for(int i=;i<=n;i++) printf("%d: %d\n",i,ans[i]);
     }
     return ;
 }

 // POJ 2398和2318差不多 多了排序和统计输出
 
 #include <cstdio>
 #include <cstring>
 #include <iostream>
 #include <algorithm>
 #include <map>
 #include <set>
 #include <queue>
 #include <stdlib.h>
 #include <cmath>
 using namespace std;
 typedef long long LL;
 const LL inf = 1e18;
 const int N = ;
 
 struct Point{
     int x,y;
     Point(){}
     Point(int _x,int _y){
         x=_x;y=_y;
     }
     Point operator -(const Point &b)const{
         return Point(x-b.x,y-b.y);
     }
     int operator *(const Point &b)const{
         return x*b.x+y*b.y;
     }
     int operator ^(const Point &b)const{
         return x*b.y-y*b.x;
     }
 };
 
 struct Line{
     Point s,e;
     Line(){}
     Line(Point _s,Point _e){
         s=_s,e=_e;
     }
 };
 
 int xmult(Point p0,Point p1,Point p2){
     return (p1-p0)^(p2-p0);
 }
 
 bool cmp(Line a,Line b){
     return a.s.x<b.s.x;
 }
 
 Line line[N];
 int ans[N];
 int num[N];
 int main(){
     int n,m,x1,y1,x2,y2;
     while(~scanf("%d",&n)&&n){
         memset(num,,sizeof(num));
         scanf("%d%d%d%d%d",&m,&x1,&y1,&x2,&y2);
         for(int i=;i<n;i++){
             int x,y;
             scanf("%d%d",&x,&y);
             line[i]=Line(Point(x,y1),Point(y,y2));
         }
         line[n]=Line(Point(x2,y1),Point(x2,y2));
         sort(line,line+n+,cmp);
         int x,y;
         Point p;
         memset(ans,,sizeof(ans));
         int tem;
         while(m--){
             scanf("%d%d",&x,&y);
             p = Point(x,y);
             int l=,r=n,mid;
             while(l<=r){
                 mid=(l+r)>>;
                 if(xmult(p,line[mid].s,line[mid].e)<){
                     tem=mid;
                     r=mid-;
                 }
                 else l=mid+;
             }
             ans[tem]++;
         }
         for(int i=;i<=n;i++){
             num[ans[i]]++;
         }
         printf("Box\n");
         for(int i=;i<=n;i++) {
             if(num[i]>)
             printf("%d: %d\n",i,num[i]);
         }
     }
     return ;
 }