Submission #765031

#	Time	Username	Problem	Language	Result	Execution time	Memory
765031		SanguineChameleon	Towns (IOI15_towns)	C++17	100 / 100	20 ms	904 KiB

towns

#include "towns.h"
#include <bits/stdc++.h>
using namespace std;

const int maxN = 1e2 + 20;
int memo[maxN][maxN];
int depth[maxN];

int dist(int u, int v) {
	if (memo[u][v] != -1) {
		return memo[u][v];
	}
	else {
		return memo[u][v] = memo[v][u] = getDistance(u, v);
	}
}

bool equal(int u, int v) {
	if (u == v) {
		return true;
	}
	else if (u == -1 || v == -1) {
		return false;
	}
	else {
		return depth[u] + depth[v] != dist(u, v);
	}
}

bool check(vector<int> comp) {
	vector<int> bucket;
	vector<int> list;
	for (auto u: comp) {
		if (list.empty() || !equal(list.back(), u)) {
			list.push_back(u);
			if (!bucket.empty()) {
				list.push_back(bucket.back());
				bucket.pop_back();
			}
		}
		else {
			bucket.push_back(u);
		}
	}
	int u = list.back();
	while (!list.empty()) {
		int v = list.back();
		list.pop_back();
		if (equal(u, v)) {
			if (!list.empty()) {
				list.pop_back();
			}
			else {
				bucket.push_back(v);
			}
		}
		else {
			if (bucket.empty()) {
				return true;
			}
			bucket.pop_back();
		}
	}
	return bucket.empty();
}

int hubDistance(int N, int sub) {
	for (int i = 0; i < N; i++) {
		for (int j = 0; j < N; j++) {
			memo[i][j] = (i == j ? 0 : -1);
		}
	}
	int X = 0;
	for (int i = 0; i < N; i++) {
		if (dist(0, i) > dist(0, X)) {
			X = i;
		}
	}
	int Y = 0;
	for (int i = 0; i < N; i++) {
		if (dist(X, i) > dist(X, Y)) {
			Y = i;
		}
	}
	int R = dist(X, Y);
	map<int, vector<int>> comps;
	for (int i = 0; i < N; i++) {
		depth[i] = (dist(X, i) + dist(0, i) - dist(X, 0)) / 2;
		int left = dist(X, i) - depth[i];
		int right = dist(X, Y) - left;
		comps[left].push_back(i);
		R = min(R, max(left, right));
	}
	int pref = 0;
	int suf = N;
	for (auto p: comps) {
		suf -= (int)p.second.size();
		if (max(p.first, dist(X, Y) - p.first) == R && pref <= N / 2 && suf <= N / 2) {
			if ((int)p.second.size() <= N / 2) {
				return R;
			}
			else {
				p.second.resize(N, -1);
				if (check(p.second)) {
					return R;
				}
			}
		}
		pref += (int)p.second.size();
	}
	return -R;
}

Compilation message (stderr)

towns.cpp: In function 'int hubDistance(int, int)':
towns.cpp:67:28: warning: unused parameter 'sub' [-Wunused-parameter]
   67 | int hubDistance(int N, int sub) {
      |                        ~~~~^~~

• Subtask 1: 13 / 13
• Subtask 2: 12 / 12
• Subtask 3: 13 / 13
• Subtask 4: 10 / 10
• Subtask 5: 13 / 13
• Subtask 6: 39 / 39