Submission #816916

#	Time	Username	Problem	Language	Result	Execution time	Memory
816916		Jarif_Rahman	Meetings (IOI18_meetings)	C++17	17 / 100	66 ms	5252 KiB

meetings

#include "meetings.h"
#include <bits/stdc++.h>
#define pb push_back
#define f first
#define sc second
using namespace std;
typedef long long int ll;
typedef string str;

struct segtree{
    int k;
    vector<int> mx;
    segtree(int n){
        k = 1;
        while(k < n) k*=2;
        mx.assign(2*k, 0);
    }
    void update(int i, int x){
        i+=k;
        mx[i] = x;
        i/=2;
        while(i){
            mx[i] = max(mx[2*i], mx[2*i+1]);
            i/=2;
        }
    }
    int get(int l, int r, int nd, int a, int b){
        if(a > r || b < l) return 0;
        if(a >= l && b <= r) return mx[nd];
        int md = (a+b)/2;
        return max(get(l, r, 2*nd, a, md), get(l, r, 2*nd+1, md+1, b));
    }
    int get(int l, int r){
        return get(l, r, 1, 0, k-1);
    }
};

vector<ll> minimum_costs_subtask_nq(const vector<int>& H, const vector<int>& L, const vector<int>& R){
    int n = H.size(), q = L.size();

    vector<ll> ans(q);
    for(int qi = 0; qi < q; qi++){
        int l = L[qi], r = R[qi];
        vector<ll> costs(r-l+1, 0);

        stack<pair<ll, int>> st;
        ll c = 0;
        for(int i = l; i <= r; i++){
            while(!st.empty() && st.top().f <= H[i]){
                auto [h, j] = st.top();
                st.pop();
                if(st.empty()) c-=h*(j-l+1);
                else c-=h*(j-st.top().sc);
            }
            if(st.empty()) c+=H[i]*(i-l+1);
            else c+=H[i]*(i-st.top().sc);
            st.push({H[i], i});
            costs[i-l]+=c;
        }
        while(!st.empty()) st.pop();
        c = 0;
        for(int i = r; i >= l; i--){
            while(!st.empty() && st.top().f <= H[i]){
                auto [h, j] = st.top();
                st.pop();
                if(st.empty()) c-=h*(r-j+1);
                else c-=h*(st.top().sc-j);
            }
            if(st.empty()) c+=H[i]*(r-i+1);
            else c+=H[i]*(st.top().sc-i);
            st.push({H[i], i});
            costs[i-l]+=c;
            costs[i-l]-=H[i];
        }

        ans[qi] = *min_element(costs.begin(), costs.end());
    }

    return ans;
}

vector<ll> minimum_costs(vector<int> H, vector<int> L, vector<int> R){
    int n = H.size(), q = L.size();
    if(n <= 5000 && q <= 5000) return minimum_costs_subtask_nq(H, L, R);

    vector<int> left(n, 0), right(n, 0);
    segtree seg(n);
    for(int i = 0; i < n; i++) if(H[i] == 1) {
        left[i] = 1;
        if(i) left[i]+=left[i-1];
        seg.update(i, left[i]);
    }
    for(int i = n-1; i >= 0; i--) if(H[i] == 1){
        right[i] = 1;
        if(i+1 < n) right[i]+=right[i+1];
    }

    vector<ll> ans(q, 0);
    for(int qi = 0; qi < q; qi++){
        int l = L[qi], r = R[qi];

        if(right[l] >= r-l+1){
            ans[qi] = r-l+1;
            continue;
        }

        int a = right[l], b = left[r];
        ans[qi] = 2*(r-l+1)-max(max(a, b), seg.get(l+a, r-b));
    }

    return ans;
}

Compilation message (stderr)

meetings.cpp: In function 'std::vector<long long int> minimum_costs_subtask_nq(const std::vector<int>&, const std::vector<int>&, const std::vector<int>&)':
meetings.cpp:39:9: warning: unused variable 'n' [-Wunused-variable]
   39 |     int n = H.size(), q = L.size();
      |         ^

• Subtask 1: 0 / 4
• Subtask 2: 0 / 15
• Subtask 3: 17 / 17
• Subtask 4: 0 / 24
• Subtask 5: 0 / 40