Submission #838589

#	Time	Username	Problem	Language	Result	Execution time	Memory
838589		42kangaroo	Cat Exercise (JOI23_ho_t4)	C++17	100 / 100	866 ms	83984 KiB

Main

//
// Created by 42kangaroo on 26/08/2023.
//
#include "bits/stdc++.h"

using namespace std;

#define int long long

using g_t = vector<vector<int>>;

struct FenTr {
	vector<int> a;

	void inc(int k, int v) {
		for (int i = k + 1; i < a.size(); i += i & (-i)) {
			a[i] += v;
		}
	}

	int get(int k) {
		int res = 0;
		for (int i = k + 1; i > 0; i -= i & (-i)) {
			res += a[i];
		}
		return res;
	}
};

void dfs(int n, int p, int &t, int d, g_t &gr, vector<int> &pre, vector<int> &po, vector<int> &pa, vector<int> &de) {
	pre[n] = t++;
	pa[n] = p;
	de[n] = d;
	for (auto e: gr[n]) {
		if (e == p) continue;
		dfs(e, n, t, d + 1, gr, pre, po, pa, de);
	}
	po[n] = t++;
}

g_t binJT(vector<int> &pa) {
	g_t binT(20, vector<int>(pa.size()));
	binT[0] = pa;
	for (int i = 1; i < 20; ++i) {
		for (int j = 0; j < pa.size(); ++j) {
			binT[i][j] = binT[i - 1][binT[i - 1][j]];
		}
	}
	return binT;
}

int up(int a, int k, g_t& binT) {
	for (int i = 0; k; k >>= 1, i++) {
		if (k & 1) a = binT[i][a];
	}
	return a;
}

int lca(int a, int b, g_t &binT, vector<int> &de) {
	if (de[a] < de[b]) swap(a, b);
	int k = de[a] - de[b];
	a = up(a, k, binT);
	if (a == b) return a;
	for (int i = 19; i >= 0; --i) {
		if (binT[i][a] != binT[i][b]) {
			a = binT[i][a];
			b = binT[i][b];
		}
	}
	return binT[0][a];
}

int findFirst(int a, FenTr &tr, vector<int> &pr, g_t &binT) {
	int num = tr.get(pr[a]);
	for (int i = 19; i >= 0; --i) {
		if (tr.get(pr[binT[i][a]]) == num) a = binT[i][a];
	}
	return a;
}

signed main() {
	ios_base::sync_with_stdio(false);
	cin.tie(nullptr);
	int n;
	cin >> n;
	vector<int> h(n);
	g_t gr(n);
	int ro = 0;
	for (int i = 0; i < n; ++i) {
		cin >> h[i];
		if (h[i] == n) ro = i;
	}
	for (int i = 0; i < n - 1; ++i) {
		int a, b;
		cin >> a >> b;
		gr[--a].push_back(--b);
		gr[b].push_back(a);
	}
	vector<int> pre(n), po(n), pa(n), de(n);
	int t = 0;
	dfs(ro, ro, t, 0, gr, pre, po, pa, de);
	g_t binT = binJT(pa);
	FenTr tr{vector<int>(2 * n + 2, 0)};
	vector<int> o(n);
	std::iota(o.begin(), o.end(),0);
	std::sort(o.begin(), o.end(), [&](int l, int r) {return h[l] > h[r];});
	vector<int> dom(n, -1);
	vector<int> fiDe(n, -1);
	fiDe[ro] = 0;
	for (int i = 1; i < n; ++i) {
		int v = o[i];
		int fi = findFirst(v, tr, pre, binT);
		int und = up(v, de[v] - de[fi] - 1, binT);
		if (dom[und] != -1) {
			fi = dom[und];
		}
		fiDe[v] = fiDe[fi] + de[v] + de[fi] - 2*de[lca(v, fi, binT, de)];
		dom[und] = v;
		tr.inc(pre[v], 1);
		tr.inc(po[v], -1);
	}
	cout << *max_element(fiDe.begin(), fiDe.end());
}

Compilation message (stderr)

Main.cpp: In member function 'void FenTr::inc(long long int, long long int)':
Main.cpp:16:25: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   16 |   for (int i = k + 1; i < a.size(); i += i & (-i)) {
      |                       ~~^~~~~~~~~~
Main.cpp: In function 'g_t binJT(std::vector<long long int>&)':
Main.cpp:45:21: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   45 |   for (int j = 0; j < pa.size(); ++j) {
      |                   ~~^~~~~~~~~~~

• Subtask 1: 7 / 7
• Subtask 2: 7 / 7
• Subtask 3: 7 / 7
• Subtask 4: 10 / 10
• Subtask 5: 20 / 20
• Subtask 6: 23 / 23
• Subtask 7: 26 / 26