Submission #96212

#	Time	Username	Problem	Language	Result	Execution time	Memory
96212		easrui	Mobile (BOI12_mobile)	C++14	0 / 100	1091 ms	86552 KiB

mobile

#include <bits/stdc++.h>
using namespace std;
const int MN = 1e6+5;
int N,L,C[MN],num[MN],cur,pos;
long double X[MN],Y[MN],A[MN],B[MN],Ipos[MN],x,ans=0,tmp;

bool cmp(int a, int b)
{
    if(A[a]==A[b]) return B[a]<B[b];
    return A[a]>A[b];
}

double getI(int a, int b)
{
    if(A[a]==A[b]) return L;
    return (B[a]-B[b])/(A[b]-A[a]);
}

int main()
{
    //freopen("C:\\Users\\user\\Desktop\\input.txt","r",stdin);
    cin >> N >> L;
    for(int i=0; i<N; i++){
        cin >> X[i] >> Y[i];
        A[i] = -2*X[i];
        B[i] = X[i]*X[i]+Y[i]*Y[i];
        num[i] = i;
    }
    sort(num,num+N,cmp);
    Ipos[pos] = 0;
    C[pos] = num[0];
    for(int i=1; i<N; i++){
        cur = num[i];
        //cout << cur << '\n';
        while(1){
            x = getI(C[pos],cur);
            if(x>=L) break;
            if(x>Ipos[pos]){
                Ipos[++pos] = x;
                C[pos] = cur;
                break;
            }
            pos--;
        }
    }
    Ipos[pos+1] = L;
    for(int i=0; i<=pos; i++){
        cur = C[i];
        //cout << X[cur] << '\n';
        tmp = max((Ipos[i]-X[cur])*(Ipos[i]-X[cur]),(Ipos[i+1]-X[cur])*(Ipos[i+1]-X[cur]))+Y[cur]*Y[cur];
        /*if(X[cur]<Ipos[i]) tmp = (Ipos[i]-X[cur])*(Ipos[i]-X[cur])+Y[cur]*Y[cur];
        else if(X[cur]>Ipos[i]) tmp = (Ipos[i+1]-X[cur])*(Ipos[i+1]-X[cur])+Y[cur]*Y[cur];
        else tmp = B[cur];*/
        ans = max(ans,tmp);
    }
    cout << sqrt(ans);
}

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