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| #include <bits/stdc++.h>
#define int long long
#define endl '\n'
#define ff double
using namespace std;
const int N = 2e5 + 7;
const ff eps = 1e-9;
ff x[N], y[N];
struct point {
ff x,y;
};
bool pointInBox(point a,point b,point p) {
ff minx = min(a.x,b.x), maxx = max(a.x,b.x);
ff miny = min(a.y,b.y), maxy = max(a.y,b.y);
return p.x >= minx && p.x <= maxx && p.y >= miny && p.y <= maxy;
}
struct sgt{
point p1,p2;
bool contains(point &p) {
return pointInBox(p1,p2,p);
}
};
struct line {
double a,b,c;
line(ff a = 0,ff b = 0, ff c = 0) : a(a), b(b), c(c) {}
};
line getLine(ff x1, ff y1, ff x2, ff y2) {
return line(y2 - y1, x1 - x2, y1 *(x2 - x1) - x1 * (y2 - y1));
}
line getLine(point p,point q) {
return getLine(p.x,p.y,q.x,q.y);
}
point getinter(line p,line q) {
point pi;
pi.x = (q.c * p.b - p.c * q.b) / ( p.a * q.b - q.a * p.b);
pi.y = (q.c * p.a - p.c * q.a) / (p.b * q.a - q.b * p.a);
return pi;
}
ff cp(point a,point b,point c) {
return (b.x - a.x) * (c.y - a.y) - (b.y - a.y) * (c.x - a.x);
}
point pi;
bool ininter(sgt s1, sgt s2) {
line p = getLine(s1.p1,s1.p2), q = getLine(s2.p1,s2.p2);
if (fabs(p.a * q.b - q.a * p.b) < eps) {
if (fabs(cp(s1.p1,s1.p2,s2.p1)) < eps) {
return s1.contains(s2.p1) || s1.contains(s2.p2);
return false;
}
}
pi = getinter(p,q);
return s1.contains(pi);
}
vector<point>num[N];
point st;
ff dist(point a,point b) {
ff dx = a.x - b.x, dy = a.y - b.y;
return sqrt(dx * dx + dy * dy);
}
bool cmp(point a, point b)
{
return dist(a,st) < dist(b,st);
}
signed main() {
int n, m;
cin >> n >> m;
ff sx, sy, tx, ty;
cin >> sx >> sy >> tx >> ty;
line star = getLine({sx,sy},{tx,ty});
sgt start = {{sx,sy},{tx,ty}};
st = {sx,sy};
for(int i = 1; i <= n; i++)
{
cin >> x[i] >> y[i];
}
for(int i = 1; i <= n; i++)
{
for(int j = 1; j <= n; j++)
{
if(i == j) continue;
sgt now = {{x[i],y[i]},{x[j],y[j]}};
if (ininter(start,now)) {
num[i].push_back({pi});
}
}
}
for (int i = 1; i <= n; ++ i ) {
sort(num[i].begin(), num[i].end(), cmp);
}
while(m--)
{
int x, y;
cin >> x >> y;
if(num[x].size() < y) cout << -1 << endl;
else printf("%.7lf %.7lf\n", num[x][y - 1].x, num[x][y - 1].y);
}
return 0;
}
|
