题解
感谢小迪给我讲题啊，这题小迪写挺好的我就不写了吧
小迪的题解
代码
#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <ctime>
#include <vector>
#include <set>
//#define ivorysi
#define eps 1e-8
#define mo 974711
#define pb push_back
#define mp make_pair
#define pii pair<int,int>
#define fi first
#define se second
#define MAXN 10005
#define space putchar(\' \')
#define enter putchar(\'\\n\')
using namespace std;
typedef long long int64;
typedef unsigned int u32;
typedef unsigned long long u64;
typedef double db;
const int64 MOD = 1000000007;
template<class T>
void read(T &res) {
res = 0;char c = getchar();T f = 1;
while(c < \'0\' || c > \'9\') {
if(c == \'-\') f = -1;
c = getchar();
}
while(c >= \'0\' && c <= \'9\') {
res = res * 10 + c - \'0\';
c = getchar();
}
res *= f;
}
template<class T>
void out(T x) {
if(x < 0) putchar(\'-\');
if(x >= 10) {
out(x / 10);
}
putchar(\'0\' + x % 10);
}
int N;
db E,s[MAXN],k[MAXN],v[MAXN];
db getv(db x,int id) {
db l = max(0.0,v[id]),r = 100000;
int cnt = 50;
db t = -1 / x;
while(cnt--) {
db mid = (l + r) / 2;
if(mid * mid * (mid - v[id]) * 2 * k[id] <= t) l = mid;
else r = mid;
}
return l;
}
db calc(db x) {
db res = 0;
for(int i = 1 ; i <= N ; ++i) {
db t = getv(x,i);
res += k[i] * s[i] * (t - v[i]) * (t - v[i]);
}
return res;
}
void Solve() {
scanf("%d%lf",&N,&E);
for(int i = 1 ; i <= N ; ++i) {
scanf("%lf%lf%lf",&s[i],&k[i],&v[i]);
}
int cnt = 100;
db L = -100000,R = 0;
while(cnt--) {
db MID = (L + R) / 2;
if(calc(MID) <= E) L = MID;
else R = MID;
}
db ans = 0;
for(int i = 1 ; i <= N ; ++i) {
ans += s[i] / getv(L,i);
}
printf("%.6lf\\n",ans);
}
int main() {
#ifdef ivorysi
freopen("f1.in","r",stdin);
#endif
Solve();
return 0;
}