제출 #284369

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
284369		user202729	Shortcut (IOI16_shortcut)	C++17	71 / 100	2083 ms	1792 KiB

shortcut

// moreflags=grader.cpp
// 16
#include "shortcut.h"
#include<vector>
#include<numeric>
#include<algorithm>
#include<cstdint>
#include<climits>
#if not LOCAL
#define NDEBUG
#endif
#include<cassert>


long long find_shortcut(int n, std::vector<int> l, std::vector<int> d, int c)
{
	std::vector<int64_t> pos; pos.reserve(n);
	pos.push_back(0);
	/*
	pos.insert(pos.end(), begin(l), end(l));
	std::partial_sum(++begin(pos), end(pos), ++pos.begin(), 0);
	*/
	std::inclusive_scan(begin(l), end(l), std::back_inserter(pos), std::plus<>(), (int64_t)0);
	// it's very rare for C++ to have just the right built-in.
	// Languages with better support for functional programming is better in this regard...
	// (Rust, Kotlin (I think?), Haskell, Python (list comprehension, although it's more verbose),
	// JavaScript (a little. Notably, integer range is missing), ...)
	// Ranges v3 will be merged into C++ soon...


	int64_t result{};
	for(auto it: l) result+=it;
	result+=2**std::max_element(begin(d), end(d));
	l.clear();

	auto const check=[&](int64_t const result){
		std::array<int64_t, 4> bounds{{0, INT64_MAX, 0, INT64_MAX}};
		// sum (minimum, maximum), difference (minimum, maximum)

		for(int b=1; b<n; ++b)
			for(int a=0; a<b; ++a){
				auto const sum=pos[a]+pos[b], diff=pos[b]-pos[a];
				assert(diff>0);
				if(d[a]+d[b]+diff>result){
					auto const rad=result-c-d[a]-d[b];
					if(rad<0) return false;
					bounds={{
						std::max(bounds[0], sum-rad),
							std::min(bounds[1], sum+rad),
							std::max(bounds[2], diff-rad),
							std::min(bounds[3], diff+rad)
					}};
					if(bounds[0]>bounds[1] or bounds[2]>bounds[3]) return false;
				}
			}

		if(bounds[1]==INT64_MAX) return true; // no bound. (result >=old diameter?)
		for(auto p: pos){
			auto const l=std::max(bounds[0]-p, bounds[2]+p), r=std::min(bounds[1]-p, bounds[3]+p);
			if(l<=r){
				auto const iterator=std::lower_bound(begin(pos), end(pos), l);
				if(iterator!=pos.end() and *iterator<=r)
					return true; // found a point
			}
		}
		return false;
	};

	for(int64_t step=(int64_t)1<<(63^__builtin_clzll(result)); step; step>>=1)
		if(result-step>0 and check(result-step))
			result-=step;
	return result;
}

• Subtask 1: 9 / 9
• Subtask 2: 14 / 14
• Subtask 3: 8 / 8
• Subtask 4: 7 / 7
• Subtask 5: 33 / 33
• Subtask 6: 0 / 22
• Subtask 7: 0 / 4
• Subtask 8: 0 / 3