Flowers 三分

 1 /********************************
 2 please don‘t hack me!! /(ToT)/~~
 3                 __------__
 4               /~          ~ 5              |    //^\\//^\|
 6            /~~\  ||  T| |T|:~ 7           | |6   ||___|_|_||:|
 8            \__.  /      o  \/‘
 9             |   (       O   )
10    /~~~~\    `\  \         /
11   | |~~\ |     )  ~------~`12  /‘ |  | |   /     ____ /~~~)13 (_/‘   | | |     /‘    |    ( |
14        | | |     \    /   __)/ 15        \  \ \      \/    /‘ \   `16          \  \|\        /   | |\___|
17            \ |  \____/     | |
18            /^~>  \        _/ <
19           |  |         \       20           |  | \        \        21           -^-\  \       |        )
22                `\_______/^\______/
23 ************************************/
24 
25 #include <iostream>
26 #include <cstdio>
27 #include <cstring>
28 #include <cmath>
29 #include <algorithm>
30 #include <string>
31 #include <vector>
32 #include <set>
33 #include <map>
34 #include <queue>
35 #include <stack>
36 #include <cstdlib>
37 #include <sstream>
38 using namespace std;
39 typedef long long LL;
40 const LL INF = 0x5fffffff;
41 const double EXP = 1E-8;
42 const LL MOD = (LL)1E9+7;
43 const int MS = 100005;
44 
45 struct node {
46     double vw,pf,vf,th;
47 }nodes[MS];
48 
49 int main() {
50     int T, N;
51     double pw;
52     while (scanf("%d",&N) == 1) {
53         if (N == 0)
54             break;
55         scanf("%lf",&pw);
56         for (int i = 0; i < N; i++) {
57             scanf("%lf%lf%lf%lf",&nodes[i].vw,&nodes[i].pf,&nodes[i].vf,&nodes[i].th);
58         }
59         double l = 0;            //枚举水量
60         double r = 101;
61         double sum1, sum2;
62         // 用三分的次数代替浮点数的比较。
63         for (int time = 1; time < 200; time++) {
64             double mid = l + (r - l) / 3;
65             double mmid = r - (r - l) / 3;
66             sum1 = mid * pw;
67             sum2 = mmid * pw;
68             for (int i = 0; i< N;i++) {
69                 double t = nodes[i].th - mid * nodes[i].vw;
70                 if(t <= 0)
71                     continue;
72                 sum1 +=  t / nodes[i].vf * nodes[i].pf;
73             }
74             for (int i = 0; i< N;i++) {
75                 double t = nodes[i].th - mmid * nodes[i].vw;
76                 if(t <= 0)
77                     continue;
78                 sum2 +=  t / nodes[i].vf * nodes[i].pf;
79             }
80             if (sum1 > sum2)
81                 l = mid;
82             else
83                 r = mmid;
84         }
85         printf("%.5lf\n",sum1);
86     }
87     return 0;
88 }