poj 2398 （计算几何）

    #include <iostream> 
    #include <stdio.h> 
    #include <string.h> 
    #include <algorithm> 

    using namespace std;  

    struct Point  
    {  
        long long int x, y;  
    };  

    struct Line  
    {  
        Point a, b;  
    } line[5005];  

    long long int cnt[1005], cnt1[1010];  

    int Multi(Point p1, Point p2, Point p0)  
    {  
        return (p1.x - p0.x) * (p2.y - p0.y) - (p2.x - p0.x) * (p1.y - p0.y);  
    }  

    bool comp (Line a, Line b)  
    {  
        return a.a.x < b.a.x;  
    }  

    void BinarySearch(Point a, int n)  
    {  
        int l, r, mid;  

        l = 0; r = n - 1;  

        while (l < r)  
        {  
            mid = (l + r) >> 1;  
            if (Multi(a, line[mid].a, line[mid].b) > 0)  
            {  
                l = mid + 1;  
            }  
            else  
            {  
                r = mid;  
            }  
        }  
        if (Multi(a, line[l].a, line[l].b) < 0)  
        {  
            cnt[l]++;  
        }  
        else  
        {  
            cnt[l + 1]++;  
        }  
    }  

    int main()  
    {  
        int n, m, x1, y1, x2, y2;  
        int i, t1, t2;  
        Point a;  

        while (cin >> n && n)  
        {  
            cin >> m >> x1 >> y1 >> x2 >> y2;  
            for (i = 0; i < n; i++)  
            {  
                cin >> t1 >> t2;  
                line[i].a.x = t1;  
                line[i].a.y = y1;  
                line[i].b.x = t2;  
                line[i].b.y = y2;  
            }  

            sort(line, line + n, comp);  

            memset(cnt, 0, sizeof (cnt));  
            memset(cnt1, 0, sizeof(cnt1));  
            for (i = 0; i < m; i++)  
            {  
                cin >> a.x >> a.y;  
                BinarySearch(a, n);  
            }  

            cout << "Box" << endl;  
            for (int i = 0; i <= n; i++)  
            {  
                if (cnt[i])  
                {  
                    cnt1[cnt[i]]++;  
                }  
            }  
            for (int i = 1; i <= m; i++)  
            {  
                if (cnt1[i])  
                {  
                    printf("%d: %I64d\n", i, cnt1[i]);  
                }  
            }  
        }  
    }