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 = 5000;

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("
");
        scanf("%d%d%d%d%d",&m,&x1,&y1,&x2,&y2);
        for(int i=0;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,0,sizeof(ans));
        int tem;
        while(m--){
            scanf("%d%d",&x,&y);
            p = Point(x,y);
            int l=0,r=n,mid;
            while(l<=r){
                mid=(l+r)>>1;
                if(xmult(p,line[mid].s,line[mid].e)<0){
                    tem=mid;
                    r=mid-1;
                }
                else l=mid+1;
            }
            ans[tem]++;
        }
        for(int i=0;i<=n;i++) printf("%d: %d
",i,ans[i]);
    }
    return 0;
}

// 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 = 5000;

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,0,sizeof(num));
        scanf("%d%d%d%d%d",&m,&x1,&y1,&x2,&y2);
        for(int i=0;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+1,cmp);
        int x,y;
        Point p;
        memset(ans,0,sizeof(ans));
        int tem;
        while(m--){
            scanf("%d%d",&x,&y);
            p = Point(x,y);
            int l=0,r=n,mid;
            while(l<=r){
                mid=(l+r)>>1;
                if(xmult(p,line[mid].s,line[mid].e)<0){
                    tem=mid;
                    r=mid-1;
                }
                else l=mid+1;
            }
            ans[tem]++;
        }
        for(int i=0;i<=n;i++){
            num[ans[i]]++;
        }
        printf("Box
");
        for(int i=1;i<=n;i++) {
            if(num[i]>0)
            printf("%d: %d
",i,num[i]);
        }
    }
    return 0;
}