Submission #784876

#	Time	Username	Problem	Language	Result	Execution time	Memory
784876		TheSahib	The Big Prize (IOI17_prize)	C++14	100 / 100	87 ms	16072 KiB

prize

#include "prize.h"
#include <bits/stdc++.h>
 
using namespace std;
 
const int BLOCK = 500;
const int MAX = 2e5 + 5;
 
int tree[MAX];
 
void update(int pos, int val){
    while(pos < MAX){
        tree[pos] += val;
        pos += pos & (-pos);
    }
}
 
int ask(int l, int r){
    if(r < l) return 0;
    if(l != 1) return ask(1, r) - ask(1, l - 1);
    int ans = 0;
    while(r > 0){
        ans += tree[r];
        r -= r & (-r);
    }
    return ans;
}
 
vector<int> mp[MAX];
 
vector<int> query(int i){
    if(!mp[i].empty()) return mp[i];
    return mp[i] = ask(i - 1);
}
 
 
int find_best(int n) {
    vector<int> order(n);
    srand(time(0));
    iota(order.begin(), order.end(), 1);
    random_shuffle(order.begin(), order.end());
    random_shuffle(order.begin(), order.end());

    vector<int> a;
    int cnt = 0;
    
    set<int> st;
    for (int i = 0; i < n; i++)
    {
        st.insert(i + 1);
    }
    for (int j = 0; j < min(1, n); ++j)
    {
        int i = order[j];
        a = query(i);
        if(a[0] + a[1] == 0) return i - 1;
        if(a[0] + a[1] < cnt){
            update(i, 1);
            st.erase(i);
        }
        else{
            cnt = a[0] + a[1];
        }
    }
    vector<int> blocks;
    int c = 1;
    while(true){
        auto itr = st.lower_bound(c);
        bool end = false;
        if(itr == st.end()){
            --itr;
            end = true;
        }
        a = query(*itr);
        if(a[0] + a[1] == 0) return (*itr) - 1;
        if(a[0] + a[1] < cnt){
            update(*itr, 1);
            st.erase(itr);
            continue;
        }
        c = *itr;
        blocks.push_back(c);
        c += MAX;
        if(end){
            break;
        }
    }

    for(int i = 0; i < blocks.size() - 1; ++i){
        int b1 = blocks[i], b2 = blocks[i + 1];
        while(query(b1)[1] - query(b2)[1] - ask(b1, b2) > 0){
            int l = b1, r = b2;
            while(l <= r){
                int x = (l + r) / 2;
                auto itr = st.lower_bound(x);
                if(itr == st.end() || (*itr) > r){
                    --itr;
                }
                int mid = *itr;

                a = query(mid);

                if(a[0] + a[1] == 0){
                    return mid - 1;
                }
                if(a[0] + a[1] < cnt){
                    update(mid, 1);
                    st.erase(mid);
                    break;
                }
                a[0] -= query(b1)[0] + ask(b1, mid);
                a[1] -= query(b2)[1] + ask(mid, b2);
    
                if(a[1] > 0){
                    l = mid + 1;
                }
                else{
                    r = mid - 1;
                }
            }
        }
    }
}

Compilation message (stderr)

prize.cpp: In function 'int find_best(int)':
prize.cpp:89:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   89 |     for(int i = 0; i < blocks.size() - 1; ++i){
      |                    ~~^~~~~~~~~~~~~~~~~~~
prize.cpp:38:24: warning: control reaches end of non-void function [-Wreturn-type]
   38 |     vector<int> order(n);
      |                        ^

• Subtask 1: 20 / 20
• Subtask 2: 80 / 80