Submission #941566

#	Time	Username	Problem	Language	Result	Execution time	Memory
941566		shoryu386	A Difficult(y) Choice (BOI21_books)	C++17	10 / 100	1 ms	344 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;
		}
	}
	
	
	ll sum = 0; vector<int> indices;
	
	for (int x = ans; x < ans + K; x++){
		sum += skim(x); indices.push_back(x);
	}
	
	if (ans != N+1-K) assert(sum >= A);
	
	
	
	
	if (sum <= 2LL*A){
		answer(indices);
	}
	else{
		impossible();
	}
}

• 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