Submission #521396

#	Time	Username	Problem	Language	Result	Execution time	Memory
521396		pavement	A Difficult(y) Choice (BOI21_books)	C++17	100 / 100	2 ms	320 KiB

books

#include "books.h"
#include <bits/stdc++.h>
using namespace std;

typedef long long ll;

ll pf[100005];
map<int, ll> mem;

ll qry(int x) {
	if (mem.find(x) != mem.end()) return mem[x];
	return mem[x] = skim(x);
}

void solve(int N, int K, ll A, int S) {
	int lo = 1, hi = N, ans = -1;
	while (lo <= hi) {
		int mid = (lo + hi) / 2;
		if (qry(mid) >= A) ans = mid, hi = mid - 1;
		else lo = mid + 1;
	}
	if (ans != -1 && ans < K) impossible();
	if (ans != -1) {
		ll cum = qry(ans);
		vector<int> vec;
		for (int i = 1; i < K; i++) cum += qry(i);
		if (A <= cum && cum <= 2 * A) {
			for (int i = 1; i < K; i++) vec.push_back(i);
			vec.push_back(ans);
			answer(vec);
			return;
		} else N = ans - 1;
	}
	ll cum = 0;
	vector<int> vec;
	for (int i = 1; i <= K; i++) pf[i] = pf[i - 1] + qry(i);
	if (A <= pf[K] && pf[K] <= 2 * A) {
		for (int i = 1; i <= K; i++) vec.push_back(i);
		answer(vec);
		return;
	}
	for (int i = N; i >= N - K + 1; i--) {
		cum += qry(i);
		vec.push_back(i);
		if (A <= pf[K - (N - i + 1)] + cum && pf[K - (N - i + 1)] + cum <= 2 * A) {
			for (int j = 1; j <= K - (N - i + 1); j++) vec.push_back(j);
			answer(vec);
			return;
		}
	}
	impossible();
}

• 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