Submission #976873

#	Time	Username	Problem	Language	Result	Execution time	Memory
976873		LucaIlie	The Big Prize (IOI17_prize)	C++17	100 / 100	28 ms	2144 KiB

prize

#include "prize.h"
#include <bits/stdc++.h>

using namespace std;

const int MAX_N = 2e5;
int ans[MAX_N][2];

int n, t;
bool found = false;
int pos;

pair<int, int> askk( int i ) {
    if ( i < 0 || i >= n )
        return { -1, -1 };

    if ( ans[i][0] == -1 ) {
        auto x = ask( i );
        ans[i][0] = x[0];
        ans[i][1] = x[1];
    }

    if ( ans[i][0] + ans[i][1] == 0 ) {
        found = true;
        pos = i;
    }

    return { ans[i][0], ans[i][1] };
}

int findMid( int &l, int &r ) {
    if ( l > r )
        return r;


    int mid = (l + r) / 2;
    while ( mid <= r && askk( mid ).first + askk( mid ).second != t && !found )
        mid++;

    if ( mid >= r ) {
        mid--;
        while ( mid >= l && askk( mid ).first + askk( mid ).second != t && !found )
            mid--;
        r = mid;
        return findMid( l, r );
    }
    return mid;
}

void solve( int l, int r, int tleft, int tright ) {
    if ( tleft == tright )
        return;

    if ( found )
        return;

    if ( l > r )
        return;

    //printf( "%d %d\n", l, r );

    int lmid = (l + r) / 2;
    while ( lmid >= l && askk( lmid ).first + askk( lmid ).second != t && !found )
        lmid--;
    int tlmid = askk( lmid ).first;

    int rmid = (l + r) / 2;
    while ( rmid <= r && askk( rmid ).first + askk( rmid ).second != t && !found )
        rmid++;
    int trmid = askk( rmid ).first;


    solve( l, lmid, tleft, tlmid );
    solve( rmid + 1, r, trmid, tright );
}

int find_best( int N ) {
    n = N;

    for ( int i = 0; i < n; i++ )
        ans[i][0] = ans[i][1] = -1;

    t = 0;
    for ( int i = 0; i < 100; i++ ) {
        int p = rand() % n;
        t = max( t, askk( p ).first + askk( p ).second );
    }

    solve( 0, n - 1, 0, t );

    // for ( int i = 0; i < n; i++ )
    //   askk( i );

    return pos;
}

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