Submission #98450

#	Time	Username	Problem	Language	Result	Execution time	Memory
98450		bogdan10bos	The Big Prize (IOI17_prize)	C++14	100 / 100	56 ms	836 KiB

prize

#include <bits/stdc++.h>

#include "prize.h"

using namespace std;

typedef pair<int, int> pii;

int sq, mxcnt, ans;
map<int, int> mp[2];

pii myask(int pos)
{
    if(mp[0].count(pos))
        return {mp[0][pos], mp[1][pos]};

    auto v = ask(pos);
    mp[0][pos] = v[0];
    mp[1][pos] = v[1];
    return {v[0], v[1]};
}

void solve(int st, int dr)
{
    if(st > dr) return;
    if(ans != -1)   return;
    auto askst = myask(st);
    auto askdr = myask(dr);

    int sumst = askst.first + askst.second;
    int sumdr = askdr.first + askdr.second;

    if(sumst == 0)  { ans = st; return; }
    if(sumdr == 0)  { ans = dr; return; }

    if(askst.second == 0 || askdr.first == 0)   return;

    if(dr - st <= 1)    return;

    if(sumst != mxcnt)
    {
        solve(st + 1, dr);
        return;
    }

    if(sumdr != mxcnt)
    {
        solve(st, dr - 1);
        return;
    }

    int cnt = askdr.first - askst.first;
    if(cnt == 0)    return;

    int lgt = dr - st - 1;

    int mij = st + (dr - st) / 2;

    solve(st, mij);
    solve(mij, dr);
}

int find_best(int N)
{
    ans = -1;
    sq = sqrt(N) + 1;
    sq = min(sq, N);
    mxcnt = 0;

    mt19937 g(chrono::high_resolution_clock::now().time_since_epoch().count());
    uniform_int_distribution<int> uid(0, N - 1);

    for(int i = 0; i - sq < N; i += sq)
    {
        int pos = min(i, N - 1);
        auto x = myask(pos);
        int sum = x.first + x.second;
        if(sum == 0)    ans = pos;
        mxcnt = max(mxcnt, sum);
    }

	for(int i = 0; i < 100; i++)
    {
        int pos = uid(g);
        auto x = myask(pos);
        int sum = x.first + x.second;
        if(sum == 0)    ans = pos;
        mxcnt = max(mxcnt, sum);
    }
    int st = 0, dr = sq;
    for(; st < N; )
    {
        solve(st, dr);
        st += sq; dr += sq;
        if(dr >= N) dr = N - 1;
    }
    return ans;
}

Compilation message (stderr)

prize.cpp: In function 'void solve(int, int)':
prize.cpp:55:9: warning: unused variable 'lgt' [-Wunused-variable]
     int lgt = dr - st - 1;
         ^~~

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