Submission #720299

#	Time	Username	Problem	Language	Result	Execution time	Memory
720299		Johann	A Difficult(y) Choice (BOI21_books)	C++14	100 / 100	2 ms	1152 KiB

books

#include <bits/stdc++.h>

#include "books.h"

using namespace std;
//
// --- Sample implementation for the task books ---
//
// To compile this program with the sample grader, place:
//     books.h books_sample.cpp sample_grader.cpp
// in a single folder and run:
//     g++ books_sample.cpp sample_grader.cpp
// in this folder.
//

typedef long long ll;
typedef vector<ll> vi;
typedef set<ll> si;
#define sz(x) (int)(x).size()

ll A;
int N, K, S;

vi store;
ll mySkim(int x)
{
    assert(1 <= x && x <= N);
    if (store[x] == -1)
        store[x] = skim(x);
    return store[x];
}
ll eval(si &ans)
{
    assert(sz(ans) == K);
    ll checkSum = 0;
    for (ll x : ans)
        checkSum += mySkim((int)x);
    return checkSum;
}

void myImpossible() { impossible(); }
void myAnswer(si &ans)
{
    assert(sz(ans) == K);
    ll checkSum = eval(ans);
    assert(A <= checkSum && checkSum <= 2 * A);
    vector<int> yourAns;
    for (ll x : ans)
        yourAns.push_back((int)x);
    answer(yourAns);
}

void solve(int _N, int _K, long long _A, int _S)
{
    A = _A, N = _N, K = _K, S = _S;
    store.assign(N + 1, -1); // starting with 1 index
    // if (S == N)              // Sub 1 & 2
    // {
    //     for (int i = 1; i <= N; ++i)
    //         mySkim(i);

    //     ll psum = 0;
    //     for (int i = 1; i <= K; ++i)
    //         psum += mySkim(i);
    //     if (psum > 2 * A)
    //         myImpossible();
    //     int idx = 1;
    //     while (idx + K <= N && psum < A)
    //     {
    //         psum -= mySkim(idx);
    //         psum += mySkim(idx + K);
    //         ++idx;
    //     }
    //     if (psum > 2 * A)
    //     {
    //         assert(mySkim(idx + K - 1) > A);
    //         si ans;
    //         for (int i = 1; i <= K - 1; ++i)
    //             ans.insert(i);
    //         ans.insert(idx + K - 1);
    //         if (eval(ans) <= 2 * A)
    //             myAnswer(ans);
    //         else
    //             myImpossible();
    //     }
    //     else if (psum >= A)
    //     {
    //         si ans;
    //         for (int i = idx; i < idx + K; ++i)
    //             ans.insert(i);
    //         myAnswer(ans);
    //     }
    //     else
    //         myImpossible();
    // }
    // else
    { // Sub 4
        ll psum = 0;
        for (int i = 1; i <= K - 1; ++i)
            psum += mySkim(i);
        if (psum + mySkim(K) > 2 * A)
        {
            myImpossible();
            return;
        }

        // binary search for first Element below 2 * A - psum
        int l = K, r = N, m;
        while (l < r)
        {
            m = (l + r + 1) / 2;
            if (mySkim(m) > 2 * A - psum)
                r = m - 1;
            else
                l = m;
        }
        psum += mySkim(l);
        if (A <= psum && psum <= 2 * A)
        {
            si ans;
            for (int i = 1; i <= K - 1; ++i)
                ans.insert(i);
            ans.insert(l);
            myAnswer(ans);
            return;
        }
        else
        {
            for (int vorne = 0; vorne <= K; ++vorne)
            {
                si ans;
                for (int i = 1; i <= vorne; ++i)
                    ans.insert(i);
                for (int i = l; i > l - K + vorne; --i)
                    ans.insert(i);
                ll check = eval(ans);
                if (A <= check && check <= 2 * A)
                {
                    myAnswer(ans);
                    return;
                }
            }
            myImpossible();
        }
    }
}

• Subtask 1: 5 / 5
• Subtask 2: 15 / 15
• Subtask 3: 10 / 10
• Subtask 4: 15 / 15
• Subtask 5: 15 / 15
• Subtask 6: 20 / 20
• Subtask 7: 20 / 20