HDU 3400 Line belt

Line belt

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 3925    Accepted Submission(s): 1524

Problem Description

 

　　In a two-dimensional plane there are two line belts, there are two segments AB and CD, lxhgww's speed on AB is P and on CD is Q, he can move with the speed R on other area on the plane.
How long must he take to travel from A to D?

 

Input

 

　　The first line is the case number T.
For each case, there are three lines.
The first line, four integers, the coordinates of A and B: Ax Ay Bx By.
The second line , four integers, the coordinates of C and D:Cx Cy Dx Dy.
The third line, three integers, P Q R.
0<= Ax，Ay，Bx，By，Cx，Cy，Dx，Dy<=1000
1<=P，Q，R<=10

 

Output

 

　　The minimum time to travel from A to D, round to two decimals.

 

Sample Input

 

1

0 0 0 100

100 0 100 100

2 2 1

 

Sample Output

 

136.60

 

三分法求解問題，奇怪的是 do{}while();過， while(){}不過；

AC代碼：

 1 # include <bits/stdc++.h>
 2 using namespace std;
 3 const double eps = 1e-5;
 4 struct Point
 5 {
 6     double x;
 7     double y;
 8 };
 9 
10 double dis(Point a, Point b)
11 {
12     return sqrt((b.y - a.y)*(b.y - a.y) + (a.x - b.x)*(a.x - b.x));
13 }
14 
15 double p, q, r;
16 double re2(Point a, Point c, Point d)
17 {
18     Point left, right;
19     Point mid, midmid;
20     double t1, t2;
21     left = c; right = d;
22     do
23     {
24         mid.x = (left.x + right.x) / 2;
25         mid.y = (left.y + right.y) / 2;
26         midmid.x = (mid.x + right.x) / 2;
27         midmid.y = (mid.y + right.y) / 2;
28         t1 = dis(a, mid) / r + dis(mid, d) / q;
29         t2 = dis(a, midmid) / r + dis(midmid, d) / q;
30         if(t1 > t2)
31             left = mid;
32         else 
33             right = midmid;
34     }
35     while(dis(left, right) >= eps);
36     return t1;
37 }
38 double re(Point a, Point b, Point c, Point d)
39 {
40     Point l, r;
41     Point mid, midmid;
42     double t1, t2;
43     l = a;
44     r = b;
45     do
46     {
47         mid.x = (l.x + r.x) / 2;
48         mid.y = (l.y + r.y) / 2;
49         midmid.x = (mid.x + r.x) / 2;
50         midmid.y = (mid.y + r.y) / 2;
51         t1 = dis(a, mid) / p + re2(mid, c, d);
52         t2 = dis(a, midmid) / p + re2(midmid, c, d);
53         if(t1 > t2)
54             l = mid;
55         else
56             r = midmid;
57     }while(dis(l, r) >= eps);
58     return t1;
59 }
60 
61 
62 int main()
63 {
64     int T;
65     scanf("%d", &T);
66     while(T--)
67     {
68         Point a, b, c, d;
69         scanf("%lf%lf%lf%lf", &a.x, &a.y, &b.x, &b.y);
70         scanf("%lf%lf%lf%lf", &c.x, &c.y, &d.x, &d.y);
71         scanf("%lf%lf%lf", &p, &q, &r);
72         
73         printf("%.2lf\n", re(a, b, c, d));
74     }
75     
76     
77     return 0;
78 }

View Code