제출 #401224

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
401224		galca	A Difficult(y) Choice (BOI21_books)	C++14	10 / 100	2 ms	1096 KiB

books

#include <iostream>
#include <vector>
using namespace std;

#include "books.h"

int findA(vector<long long>& books, long long A, int lower, int upper) {
	if (books[lower] == -1) {
		books[lower] = skim(lower + 1);
	}
	if (books[upper] == -1) {
		books[upper] = skim(upper + 1);
	}
	if (books[lower] > A) {
		return -1;
	}
	if (books[upper] <= A) {
		return upper;
	}

	if (upper - lower < 2) {
		return lower;
	}

	int half = (upper - lower + 1) / 2;
	books[lower + half] = skim(lower + half + 1);

	if (books[lower + half] <= A) return findA(books, A, lower + half, upper);
	else return findA(books, A, lower, lower + half);
}

void solve(int N, int K, long long A, int S) {
	if (K > N) {
		impossible();
		return;
	}
	vector<long long> books(N);

	for (int i = 0; i < N; i++) {
		books[i] = -1;
	}

	long long sumFirstK = 0;
	for (int i = 0; i < K; i++) {
		if (books[i] == -1) {
			books[i] = skim(i + 1);
		}
		sumFirstK += books[i];
	}

	if (sumFirstK > A * 2) {
		impossible();
	}
	else {
		vector<int> res;
		for (int i = 0; i < K; i++) {
			res.push_back(i + 1);
		}
		if (sumFirstK >= A) {
			answer(res);
		}
		else {
			// sumFirstK < A
			// find last element < A
			long long posA = findA(books, A, 0, N - 1);
			if (books[posA] == -1) {
				books[posA] = skim(posA + 1);
			} 
			// try to replace smallest with largest
			for (int i = 0; i < K; i++) {
				if (books[posA - i] == -1) {
					books[posA - i] = skim(posA - i + 1);
				}
				sumFirstK -= books[i];
				res[i] = posA - i + 1;
				sumFirstK += books[posA - i];
				if (sumFirstK >= A) {
					answer(res);
					break;
				}
			}
			// failed to build the sum with elements < A only
			// need to look at elements > A

			int i = 0;
			while ((i < K) && ((posA + 1 + i) < N)) {
				if (books[posA + i + 1] == -1) {
					books[posA + i + 1] = skim(posA + i + 2);
				}
				sumFirstK -= books[K - i - 1];
				res[K - i - 1] = posA + i + 2;
				sumFirstK += books[posA + i + 1];
				if (sumFirstK > A * 2) {
					impossible();
					break;
				}
				else {
					if (sumFirstK >= A) {
						answer(res);
						break;
					}
				}
			}
			impossible();
		}
	}
	return;
}

• Subtask 1: 0 / 5
• Subtask 2: 0 / 15
• Subtask 3: 10 / 10
• Subtask 4: 0 / 15
• Subtask 5: 0 / 15
• Subtask 6: 0 / 20
• Subtask 7: 0 / 20