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]);
}
}
}
}