1 #include<iostream>
2 #include<cstdio>
3 #include<cmath>
4 #include<algorithm>
5 #define EPS 1e-4
6 #define MAXN 50004
7 using namespace std;
8 double x[MAXN],w[MAXN];
9
10 inline double get_f1(double xx, int start, int n)
11 {
12 double sum(0);
13 for (int i(start); i<n; ++i) {
14 sum += (xx - x[i])*(xx - x[i])*w[i];
15 }
16 return sum;
17 }
18
19 inline double get_res(double xx, int n)
20 {
21 double sum(0);
22 for (int i(0); i<n; ++i) {
23 sum += fabs((xx - x[i])*(xx - x[i])*(xx - x[i]))*w[i];
24 }
25 return sum;
26 }
27
28 inline int cmp(double x)
29 {
30 if (x > EPS)return 1;
31 if (x < -EPS)return -1;
32 return 0;
33 }
34
35 int main()
36 {
37 int n;
38 int t;
39 scanf("%d",&t);
40 for (int cnt(1); cnt<=t; ++cnt) {
41 cout<<"Case #"<<cnt<<": ";
42 int n;
43 scanf("%d",&n);
44 for (int i(0); i<n; ++i) {
45 scanf("%lf%lf",&x[i],&w[i]);
46 }
47
48 double l(x[0]),r(x[n-1]),mid(0);
49 while (true) {
50 mid = (l + r)/2.0;
51 int midx = upper_bound(x,x+n,mid) - x;
52 double fir(get_f1(mid,0,midx)),sec(get_f1(mid,midx,n));
53 if (cmp(fir - sec) > 0)r = mid;
54 else if (cmp(fir - sec) < 0)l = mid;
55 else break;
56 }
57 __int64 ans = get_res(mid,n) + 0.5;
58 printf("%I64d\n",ans);
59 }
60 return 0;
61 }
View Code
