#include <cstdio>
#include <cstring>
#include <cmath>
#include <algorithm>
#include <iostream>
#define enter putchar('\n')
#define space putchar(' ')
using namespace std;
typedef long long ll;
template <class T>
void read(T &x){
    char c;
    bool op = 0;
    while(c = getchar(), c < '0' || c > '9')
        if(c == '-') op = 1;
    x = c - '0';
    while(c = getchar(), c >= '0' && c <= '9')
        x = x * 10 + c - '0';
    if(op == 1) x = -x;
}
template <class T>
void write(T x){
    if(x < 0) putchar('-'), x = -x;
    if(x >= 10) write(x / 10);
    putchar('0' + x % 10);
}

const int N = 10005, INF = 0x3f3f3f3f;
int n;
double E, s[N], k[N], u[N];

double getv(double x, int i){
    double l = max(u[i], double(0)), r = 100005, mid;
    int cnt = 60;
    while(cnt--){
        mid = (l + r) / 2;
        if(2 * k[i] * x * mid * mid * (mid - u[i]) > -s[i]) l = mid;
        else r = mid;
    }
    mid = (l + r) / 2;
    return (l + r) / 2;
}
double calc(double x){
    double sum = 0;
    for(int i = 1; i <= n; i++){
        double v = getv(x, i);
        sum += k[i] * (v - u[i]) * (v - u[i]);
    }
    return sum;
}

int main(){

    scanf("%d%lf", &n, &E);
    for(int i = 1; i <= n; i++)
        scanf("%lf%lf%lf", &s[i], &k[i], &u[i]), k[i] *= s[i];
    double l = -INF, r = 0, mid;
    int cnt = 100;
    while(cnt--){
        mid = (l + r) / 2;
        if(calc(mid) <= E) l = mid;
        else r = mid;
    }
    mid = (l + r) / 2;
    double ans = 0;
    for(int i = 1; i <= n; i++)
        ans += s[i] / getv(mid, i);
    printf("%.8lf\n", ans);

    return 0;
}

前面的基本都能A 最后一个点tle，稍微加点优化就行了
```cpp
#include<iostream>
#include<cstring>
#include<cstdio>
#define N 500010
#define inf 100000008
using namespace std;

int n;
double k[N],s[N],u[N],Eu,v[N];

bool check(double a,double b,int i){
return 2.0*a*k[i]*b*b*(b-u[i])<=1.0?true:false;
}

double TwoPoint(int i,double lambda){
double l=max(u[i],0.0),r=inf,mid;
for(int j=1;j<=100;++j){
mid=(l+r)/2;
if(check(lambda,mid,i))l=mid;
else r=mid;
}
return mid;
}

bool Check(double mid){
double E=0;
for(int i=1;i<=n;++i)v[i]=TwoPoint(i,mid);
for(int i=1;i<=n;++i)E+=k[i]*s[i]*(v[i]-u[i])*(v[i]-u[i]);
return E>=Eu;
}

int main(){
scanf("%d",&n);
scanf("%lf",&Eu);
for(int i=1;i<=n;++i)
scanf("%lf%lf%lf",&s[i],&k[i],&u[i]);
double l=0.0,r=inf,mid;
for(int j=1;j<=100;++j){
mid=(l+r)/2;
if(Check(mid))l=mid;
else r=mid;
}
double ans=0;
for(int i=1;i<=n;++i)
ans+=s[i]/v[i];
printf("%.8f\n",ans);
return 0;
}
```

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