Submission #540447

#	Time	Username	Problem	Language	Result	Execution time	Memory
540447		elazarkoren	A Difficult(y) Choice (BOI21_books)	C++17	100 / 100	3 ms	388 KiB

books

#include <bits/stdc++.h>
#include "books.h"
#define x first
#define y second
#define all(v) v.begin(), v.end()
#define chkmin(a, b) a = min(a, b)
#define chkmax(a, b) a = max(a, b)
using namespace std;
typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<int, int> pii;
typedef vector<pii> vii;
typedef vector<bool> vb;

const int MAX_N = 2e5;

ll books[MAX_N];

ll ask(int i) {
    if (books[i]) return books[i];
    return books[i] = skim(i);
}

vi Solve(int n, int k, long long a) {
    ll sum = 0;
    vi l, r;
    for (int i = 1; i <= k; i++) {
        sum += ask(i);
        l.push_back(i);
    }
    if (sum > 2 * a) {
        impossible();
        return {};
    }
    if (a <= sum) {
        return l;
    }
    for (int i = k; i; i--) {
        sum -= books[i];
        l.pop_back();
        ll x = ask(n - k + i);
        if (x + sum < a) {
            r.push_back(n - k + i);
            sum += x;
            continue;
        } else if (x + sum <= 2 * a) {
            r.push_back(n - k + i);
            for (int j : r) l.push_back(j);
            return l;
        }
        int begin = i + 1, end = n - k + i, mid;
        while (begin < end) {
            mid = (begin + end) >> 1;
            x = ask(mid);
            if (a <= sum + x && x + sum <= 2 * a) {
                r.push_back(mid);
                for (int j : r) l.push_back(j);
                return l;
            }
            if (a > sum + x) {
                begin = mid + 1;
            } else end = mid;
        }
        for (int j : r) l.push_back(j);
        return l;
    }
    return {};
}

void solve(int n, int k, long long a, int s) {
    int begin = 1, end = n + 1, mid;
    while (begin < end) {
        mid = (begin + end) >> 1;
        if (ask(mid) < a) {
            begin = mid + 1;
        } else end = mid;
    }
    vi ans = Solve(end - 1, k, a);
    if (!ans.empty()) answer(ans);
    else {
        ll sum = ask(end);
        ans.push_back(end);
        for (int i = 1; i < k; i++) {
            ans.push_back(i);
            sum += books[i];
        }
        if (a <= sum && sum <= 2 * a) answer(ans);
        else impossible();
    }
}
//6 3 20 6
//1 2 3 8 9 10

• 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