Submission #303774

#	Time	Username	Problem	Language	Result	Execution time	Memory
303774		user202729	Packing Biscuits (IOI20_biscuits)	C++17	100 / 100	33 ms	896 KiB

biscuits

// moreflags=grader.cpp
// ......

#include "biscuits.h"
#include<array>
#include<cstdint>
#include<vector>
#include<cmath>
#include<iostream>
#if not LOCAL
#define NDEBUG
#endif
#include<cassert>

struct Node{ // represents a non-strictly decreasing list of numbers
	int64_t count;
	int64_t first; // also the maximum
	int64_t delta;
	std::array<int, 2> children; // index in nodes vector, or {{-1, -1}} if count==1
};
std::vector<Node> nodes;

int deltaed(int node, int64_t delta){
	if(node<0 or delta==0) return node;
	nodes.push_back(nodes[node]);
	nodes.back().first+=delta;
	nodes.back().delta+=delta;
	return int(nodes.size()-1);
}

int append(int first, int sec, int64_t delta){
	assert(first>=0); // precondition

	if(sec==-1) return deltaed(first, delta);
	assert(sec>=0);
	nodes.push_back({
		nodes[first].count+nodes[sec].count,
			nodes[first].first+delta,
			delta,
			{{first, sec}}
	});
	return int(nodes.size()-1);
}

int prefixLargerEqual(int node, int64_t minimum){
	// return -1 if result is empty
	assert((nodes[node].count==1)==(nodes[node].children==std::array<int, 2>{{-1, -1}}));

	if(nodes[node].first<minimum) return -1;

	if(nodes[node].count==1){
		// single node
		assert(nodes[node].first==nodes[node].delta);
		return node;
	}

	auto const [a, b]=nodes[node].children;
	auto const t=minimum-nodes[node].delta;
	auto const b1=prefixLargerEqual(b, t);
	if(b1==b) return node;
	if(b1<0) return deltaed(prefixLargerEqual(a, t), nodes[node].delta);
	return append(a, b1, nodes[node].delta);
}

long long count_tastiness(long long x, std::vector<long long> a) {

	nodes.clear();
	nodes.push_back({1, a[0], a[0], {{-1, -1}}});

	int all=0; // node reference
	// initial list: {a[0]} (note that the first element will always be a[0])

	int64_t s=0;
	for(int i=0;; ++i){
		assert(nodes[all].first==a[0]);
		if(a[0]-x*std::round(std::pow(2., i))>=s){
			all=append(all, deltaed(prefixLargerEqual(all, s+(x<<i)), -(x<<i)), 0);
		}

		if(i+1<(int)a.size())
			s-=a[i+1]<<(i+1);

		if(i==(int)a.size()+62){
			return nodes[all].count;
		}
	}
}

• Subtask 1: 9 / 9
• Subtask 2: 12 / 12
• Subtask 3: 21 / 21
• Subtask 4: 35 / 35
• Subtask 5: 23 / 23