Submission #827453

#	Time	Username	Problem	Language	Result	Execution time	Memory
827453		GrindMachine	Radio Towers (IOI22_towers)	C++17	11 / 100	4059 ms	4088 KiB

towers

// Om Namah Shivaya

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;

template<typename T> using Tree = tree<T,null_type,less<T>,rb_tree_tag,tree_order_statistics_node_update>;
typedef long long int ll;
typedef long double ld;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;

#define fastio ios_base::sync_with_stdio(false); cin.tie(NULL)
#define pb push_back
#define endl '\n'
#define ff first
#define ss second
#define all(a) a.begin(),a.end()
#define rall(a) a.rbegin(),a.rend()
#define conts continue
#define sz(a) a.size()

#define rep(i,n) for(int i = 0; i < n; ++i)
#define rep1(i,n) for(int i = 1; i <= n; ++i)
#define rev(i,s,e) for(int i = s; i >= e; --i)
#define trav(i,a) for(auto &i : a)

template<typename T>
void amin(T &x, T y){
  x = min(x,y);
}

template<typename T>
void amax(T &x, T y){
  x = max(x,y);
}

#define debug(x) cout << #x << " = "; cout << x; cout << endl

const int MOD = 1e9 + 7;
const int N = 1e5 + 5;
const int inf1 = 1e9 + 5;
const ll inf2 = (ll)1e18 + 5;

#include "towers.h"

template<typename T>
struct segtree{
    struct data{
        ll a;
    };

    data d_neutral = {-inf2};

    data merge(data &left, data &right){
        data curr;
        curr.a = max(left.a,right.a);
        return curr;
    }

    void modify(int i, T v){
        tr[i].a = v;
    }

    int n;
    vector<data> tr;

    segtree(int n_){
        n = n_;
        tr.assign(2*n+5,d_neutral);
    }

    void pupd(int i, T v){
        modify(i+n,v);
        for(i = (i+n)>>1; i; i >>= 1){
            tr[i] = merge(tr[i<<1],tr[i<<1|1]);
        }
    }

    data query(int l, int r){
        data res = d_neutral;

        for(l += n, r += n; l <= r; l >>= 1, r >>= 1){
            if(l & 1){
                res = merge(res,tr[l++]);
            }
            if(!(r & 1)){
                res = merge(res,tr[r--]);
            }
        }

        return res;
    }
};

int n;
vector<int> a;

void init(int n_, std::vector<int> a_) {
    n = n_;
    a = a_;    
}

int max_towers(int L, int R, int D) {
    vector<int> b;
    for(int i = L; i <= R; ++i){
        b.pb(a[i]);
    }
    int m = sz(b);

    segtree<int> st(m+5);
    rep(i,m) st.pupd(i,b[i]);

    vector<int> lx(m,-1), rx(m,inf1);
    rep(i,m){
        int lo = 0, hi = i-1;
        while(lo <= hi){
            int mid = (lo+hi) >> 1;
            int mx = st.query(mid,i-1).a;
            if(b[i] <= mx-D){
                lx[i] = mid-1;
                lo = mid+1;
            }
            else{
                hi = mid-1;
            }
        }

        lo = i+1, hi = m-1;
        while(lo <= hi){
            int mid = (lo+hi) >> 1;
            int mx = st.query(i+1,mid).a;
            if(b[i] <= mx-D){
                rx[i] = mid+1;
                hi = mid-1;
            }
            else{
                lo = mid+1;
            }
        }
    }

    vector<int> dp(m);
    rep(i,m){
        dp[i] = 1;
        rep(j,i){
            if(j <= lx[i] and i >= rx[j]){
                amax(dp[i],dp[j]+1);
            }
        }
    }

    int ans = *max_element(all(dp));
    return ans;
}

• Subtask 1: 0 / 4
• Subtask 2: 11 / 11
• Subtask 3: 0 / 12
• Subtask 4: 0 / 14
• Subtask 5: 0 / 17
• Subtask 6: 0 / 19
• Subtask 7: 0 / 23