Submission #941620

#	Time	Username	Problem	Language	Result	Execution time	Memory
941620		shoryu386	A Difficult(y) Choice (BOI21_books)	C++17	30 / 100	2760 ms	608 KiB

books

#include <bits/stdc++.h>
#include "books.h"
using namespace std;
 
void solve(int N, int K, long long A, int S) {
    // TODO implement this function
    
    //k books, sum of A
    typedef long long ll;
    
    //x, x+1, x+2, x+3, x+4, x+5... and so on
    
    int extrasum = 0;
    for (int x = 0; x < K; x++){
		extrasum += x;
	}
	
	//we want A <= x*K + extrasum <= 2*A
	//x*K + extrasum >= A
	//x*K >= A-extrasum
	//x >= (A-extrasum)/K
	
	ll target = (A - extrasum)/K + ((A - extrasum)%K != 0);
	//to do: check rounding
	
	if (A - extrasum <= 0) {impossible(); return;}
	
	int l = 1, r = N+1-K, ans = N+1-K;
	while (l <= r){
		int m = (l+r)/2;
		
		ll res = skim(m);
		
		if (res >= target){
			r = m-1;
			ans = m;
		}
		else{
			l = m+1;
		}
	}
	
	vector<pair<int, ll>> items; set<int> indicesInside;
	for (int x = max(1, ans-10); x < min(N+1, ans+K); x++){
		items.push_back({x, skim(x)}); indicesInside.insert(x);
	}
	
	for (int x = 1; x <= 10; x++){
		if (indicesInside.count(x) == 0) items.push_back({x, skim(x)}), indicesInside.insert(x);
	}
	
	
	for (int bm = 0; bm < (1<<items.size()); bm++){
		if (__builtin_popcount(bm) != K) continue;
		
		ll sum = 0;
		for (int x = 0; x < (int)items.size(); x++){
			if (bm & (1<<x)){
				sum += items[x].second;
			}
		}
		
		if (A <= sum && sum <= 2LL*A){
			vector<int> indices;
			for (int x = 0; x < (int)items.size(); x++){
				if (bm & (1<<x)){
					indices.push_back(items[x].first);
				}
			}
			answer(indices);
			return;
		}
	}
	
	impossible();
}
 

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