Submission #994392

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Source Code Expand

#include<iostream>
#include<iomanip>
#include<map>
#include<unordered_map>
#include<set>
#include<unordered_set>
#include<vector>
#include<array>
#include<string>
#include<stack>
#include<queue>
#include<algorithm>
#include<cassert>
#include<functional>
#include<random>
#include<complex>
#include<bitset>
#include<chrono>
//#include<boost/multiprecision/cpp_int.hpp>
#define int int64_t
#define uint uint64_t
#define REP(i, a, b) for (int64_t i = (int64_t)(a); i < (int64_t)(b); i++)
#define rep(i, a) REP(i, 0, a)
#define EACH(i, a) for (auto i: a)
#define ITR(x, a) for (auto x = a.begin(); x != a.end(); x++)
#define ALL(a) (a.begin()), (a.end())
#define HAS(a, x) (a.find(x) != a.end())
#define Min(x) *min_element(ALL(x))
#define Max(x) *max_element(ALL(x))
#define Unique(L) (L.erase(unique(ALL(L)), L.end()))
#define veccat(v1, v2) std::copy((v2).begin(),(v2).end(),std::back_inserter(v1)/*v1の後ろにv2を入れる*/)
#define intmax (std::numeric_limits<int64_t>::max() / 4)
using namespace std;
//typedef boost::multiprecision::cpp_int bigint;
const double EPS = 1e-9;
const double PI = acos(-1.0);

class segtree_max_pointupdate {
private:
	typedef int T;
public:
	segtree_max_pointupdate(const int N) {
		SIZE = roundup_pow2(N);
		v.clear();
		v.resize(SIZE * 2, -INF);
	}

	//v[index]=numberとする。
	void update(const int index, const T number) {
		v[index + SIZE] = number;
		for (int i = (index + SIZE) / 2; i; i = i / 2)v[i] = max(v[i * 2], v[i * 2 + 1]);
	}

	//[index]の値を返す。
	T getnum(const int index) {
		return v[index + SIZE];
	}

	//[L,R)の最大値を返す。
	T getmax(const int L, const int R) {
		return getmax_inner(L, R, 1, 0, SIZE);
	}
private:
	T getmax_inner(const int queryL, const int queryR, const int index, const int segL, const int segR) {
		if (queryR <= segL || segR <= queryL)return -INF;
		if (queryL <= segL && segR <= queryR)return v[index];
		return max(getmax_inner(queryL, queryR, index * 2, segL, (segL + segR) / 2),
			getmax_inner(queryL, queryR, index * 2 + 1, (segL + segR) / 2, segR));
	}

	//x以上であるような2のべき乗数のうち最小のものを返す。
	int roundup_pow2(int x) {
		x--;
		rep(i, 6)x |= x >> (1LL << i);
		return x + 1;
	}

	int SIZE;
	vector<T>v;
	const static T INF = 99999999;
};


int N, A;
segtree_max_pointupdate memo(1000001);


int solve(const int speed, const int time, const int ub) {
	//現在time秒目で、1秒間にspeed枚焼けて、手持ちゼロであるときの
	//手持ちN枚にできる最短の時刻を求めて返す。
	//ただし時刻ub以降については考えない。

	if (ub <= time)return ub;
	
	int maxspeed = memo.getmax(0, time + 1);
	if (speed <= maxspeed)return ub;
	memo.update(time, speed);

	const int hold_ans = time + (N + speed - 1) / speed;
	if (hold_ans <= time + 2 + A)return hold_ans;
	int best_ans = hold_ans;
	int next_ub = min(ub, hold_ans);
	int next_time = time + 1;
	for (int i = speed * 2; i < N; i += speed) {
		next_time++;
		if (best_ans <= next_time + A)break;
		int ans = solve(i, next_time + A, next_ub);
		best_ans = min(best_ans, ans);
		next_ub = min(ub, best_ans);
	}
	return best_ans;
}

signed main() {
	cin.tie(0);
	ios::sync_with_stdio(false);

	cin >> N >> A;
	assert(N <= 1000000 && A <= 1000000);


	int ans = solve(1, 0, intmax);
	cout << ans << endl;


}

Submission Info

Judge Result