1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
|
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#define N 300
#define XMIN 2e14
#define XMAX 4e14
#define eps 1e-6
#define ABS(x) ((x)>0?(x):-(x))
typedef struct { double x, y, z; } point_t;
typedef struct { point_t p, v; } line_t;
char *buf, line[N];
int n, s;
line_t l[N];
bool isnum(char c) { return (c >= '0' && c <= '9') || c == '-'; }
line_t readl(char *buf) {
double a[6];
for (int i = 0; i < 6; i++) {
a[i] = (double)atoll(buf);
while (isnum(*buf)) buf++;
while (*buf != '\n' && !isnum(*buf)) buf++;
}
return (line_t) {
.p = (point_t){.x = a[0], .y = a[1], .z = a[2]},
.v = (point_t){.x = a[3], .y = a[4], .z = a[5]}
};
}
double det(double a, double b, double c, double d) { return a*d-b*c; }
bool parallel2d(line_t l1, line_t l2) {
double d = det(l1.v.x, l2.v.x, l1.v.y, l2.v.y);
return ABS(d) < eps;
}
point_t collide2d(line_t l1, line_t l2, double *t1, double *t2) {
double a1 = l1.v.x;
double b1 = -l2.v.x;
double c1 = l2.p.x - l1.p.x;
double a2 = l1.v.y;
double b2 = -l2.v.y;
double c2 = l2.p.y - l1.p.y;
double d = det(a1, b1, a2, b2);
*t1 = det(c1, b1, c2, b2) / d;
*t2 = det(a1, c1, a2, c2) / d;
double x = l1.p.x + l1.v.x * (*t1);
double y = l1.p.y + l1.v.y * (*t1);
return (point_t) {.x = x, .y = y};
}
int main() {
for (n = 0; (buf = fgets(line, N, stdin)) != NULL; n++)
l[n] = readl(buf);
for (int i = 0; i < n; i++) {
for (int j = i+1; j < n; j++) {
if (parallel2d(l[i], l[j])) continue;
double t1, t2;
point_t p = collide2d(l[i], l[j], &t1, &t2);
if (t1 < -eps || t2 < -eps) continue;
s += p.x > XMIN-eps && p.x < XMAX+eps &&
p.y > XMIN-eps && p.y < XMAX+eps;
}
}
printf("%d\n", s);
return 0;
}
|
