제출 #1022973

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
1022973		JakobZorz	송신탑 (IOI22_towers)	C++17	23 / 100	4083 ms	19012 KiB

towers

#include"towers.h"
#include<vector>
#include<iostream>
using namespace std;

int n;
vector<int>arr;
vector<int>thres;
vector<int>prv,nxt;
vector<vector<int>>arr_rmq;
vector<vector<int>>thres_rmq;

void init_prev(){
    prv.resize(n);
    vector<int>s;
    for(int i=0;i<n;i++){
        while(s.size()&&arr[s.back()]>arr[i])
            s.pop_back();
        if(s.empty())
            prv[i]=-1;
        else
            prv[i]=s.back();
        s.push_back(i);
    }
}

void init_nxt(){
    nxt.resize(n);
    vector<int>s;
    for(int i=n-1;i>=0;i--){
        while(s.size()&&arr[s.back()]>arr[i])
            s.pop_back();
        if(s.empty())
            nxt[i]=-1;
        else
            nxt[i]=s.back();
        s.push_back(i);
    }
}

void init_arr_rmq(){
    arr_rmq=vector<vector<int>>(20,vector<int>(n));
    arr_rmq[0]=arr;
    for(int p=1;p<20;p++){
        for(int i=0;i+(1<<p)<=n;i++){
            arr_rmq[p][i]=max(arr_rmq[p-1][i],arr_rmq[p-1][i+(1<<(p-1))]);
        }
    }
}

int get_arr_max(int l,int r){
    int pw2=2;
    int p=0;
    while(pw2<r-l){
        pw2*=2;
        p++;
    }
    pw2/=2;
    return max(arr_rmq[p][l],arr_rmq[p][r-pw2]);
}

void init_thres(){
    thres.resize(n);
    for(int i=0;i<n;i++){
        int mn=2e9;
        
        if(prv[i]!=-1){
            int mx1=get_arr_max(prv[i],i);
            mn=min(mn,mx1);
        }
        
        if(nxt[i]!=-1){
            int mx2=get_arr_max(i,nxt[i]);
            mn=min(mn,mx2);
        }
        
        thres[i]=mn-arr[i];
    }
}

void init_thres_rmq(){
    thres_rmq=vector<vector<int>>(20,vector<int>(n));
    thres_rmq[0]=thres;
    for(int p=1;p<20;p++){
        for(int i=0;i+(1<<p)<=n;i++){
            thres_rmq[p][i]=max(thres_rmq[p-1][i],thres_rmq[p-1][i+(1<<(p-1))]);
        }
    }
}

int get_thres_max(int l,int r){
    int pw2=2;
    int p=0;
    while(pw2<r-l){
        pw2*=2;
        p++;
    }
    pw2/=2;
    return max(thres_rmq[p][l],thres_rmq[p][r-pw2]);
}

void init(int N,vector<int>H){
    arr=H;
    n=(int)arr.size();
    init_prev();
    init_nxt();
    init_arr_rmq();
    init_thres();
    init_thres_rmq();
}

int max_towers(int L,int R,int D){
    int res=0;
    for(int i=L;i<=R;i++){
        if(thres[i]>=D){
            res++;
        }
    }
    
    int first=-1,last=-1;
    if(get_thres_max(L,R+1)<D){
        first=L;
        for(int i=L;i<=R;i++)
            if(arr[i]<arr[first])
                first=i;
        res=1;
        last=first;
    }else{
        {
            int l=L,r=R+1;
            while(l<r-1){
                int mid=(l+r)/2;
                if(get_thres_max(L,mid)>=D)
                    r=mid;
                else
                    l=mid;
            }
            first=l;
        }
        
        {
            int l=L,r=R+1;
            while(l<r-1){
                int mid=(l+r)/2;
                if(get_thres_max(mid,R+1)>=D)
                    l=mid;
                else
                    r=mid;
            }
            last=l;
        }
    }
    
    int mx=0;
    for(int i=first;i>=L;i--){
        if(max(arr[i],arr[first])+D<=mx){
            res++;
            break;
        }
        mx=max(mx,arr[i]);
    }
    
    mx=0;
    for(int i=last;i<=R;i++){
        if(max(arr[i],arr[last])+D<=mx){
            res++;
            break;
        }
        mx=max(mx,arr[i]);
    }
    
    return res;
}

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