Submission #764765

#	Time	Username	Problem	Language	Result	Execution time	Memory
764765		SanguineChameleon	Towns (IOI15_towns)	C++17	13 / 100	12 ms	404 KiB

towns

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

const int maxN = 1e2 + 20;
int memo[maxN][maxN];
int depth[maxN];
bool flag[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);
	}
}

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(Y, i) - dist(X, Y)) / 2;
		int left = dist(X, i) - depth[i];
		int right = dist(Y, i) - depth[i];
		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;
			}
			bool ok = true;
			for (auto u: p.second) {
				if (flag[u]) {
					continue;
				}
				flag[u] = true;
				int sz = 0;
				deque<int> q;
				q.push_back(u);
				while (!q.empty()) {
					int u = q.front();
					q.pop_front();
					sz++;
					for (auto v: p.second) {
						if (!flag[v] && depth[u] + depth[v] != dist(u, v)) {
							flag[v] = true;
							q.push_back(v);
						}
					}
				}
				if (sz > N / 2) {
					ok = false;
					break;
				}
			}
			if (ok) {
				return R;
			}
		}
		pref += (int)p.second.size();
	}
	return -R;
}

Compilation message (stderr)

towns.cpp: In function 'int hubDistance(int, int)':
towns.cpp:64:10: warning: declaration of 'u' shadows a previous local [-Wshadow]
   64 |      int u = q.front();
      |          ^
towns.cpp:55:14: note: shadowed declaration is here
   55 |    for (auto u: p.second) {
      |              ^
towns.cpp:19:28: warning: unused parameter 'sub' [-Wunused-parameter]
   19 | int hubDistance(int N, int sub) {
      |                        ~~~~^~~

• Subtask 1: 13 / 13
• Subtask 2: 0 / 12
• Subtask 3: 0 / 13
• Subtask 4: 0 / 10
• Subtask 5: 0 / 13
• Subtask 6: 0 / 39