Submission #835474

#	Time	Username	Problem	Language	Result	Execution time	Memory
835474		Valaki2	Towns (IOI15_towns)	C++14	13 / 100	14 ms	936 KiB

towns

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

const int inf = 1e6 + 42;

int n;
vector<vector<int> > storedist;

int dist(int a, int b) {
	if(storedist[a][b] != -1) {
		return storedist[a][b];
	}
	return storedist[a][b] = storedist[b][a] = getDistance(a - 1, b - 1);
}

void reset() {
	storedist.clear();
	storedist.assign(1 + n, vector<int> (1 + n, -1));
	for(int i = 1; i <= n; i++) {
		storedist[i][i] = 0;
	}
}

int hubDistance(int N, int sub) {
	n = N;
	reset();
	int ans = inf;
	int X = 1;
	for(int i = 2; i <= n; i++) {
		if(dist(1, i) > dist(1, X)) {
			X = i;
		}
	}
	int Y = X;
	for(int i = 1; i <= n; i++) {
		if(dist(X, i) > dist(X, Y)) {
			Y = i;
		}
	}
	int diam = dist(X, Y);
	for(int i = 1; i <= n; i++) {
		int a = dist(i, X);
		int b = dist(i, Y);
		int from = (a + b - diam) / 2;
		ans = min(ans, max(a - from, b - from));
	}
	bool from_X = false, from_Y = false;
	for(int i = 1; i <= n; i++) {
		if(i == X || i == Y) {
			continue;
		}
		int a = dist(i, X);
		int b = dist(i, Y);
		int from = (a + b - diam) / 2;
		if(a - from == ans) {
			from_X = true;
		} else if(b - from == ans) {
			from_Y = true;
		}
	}
	if(from_X && from_Y) {
		return ans;
	}
	vector<int> Z = {X, Y};
	int idx = 0;
	if(from_Y) {
		idx = 1;
	}
	set<int> s;
	int less_cnt = 0, more_cnt = 0;
	for(int i = 1; i <= n; i++) {
		int a = dist(i, X);
		int b = dist(i, Y);
		int from = (a + b - diam) / 2;
		vector<int> d = {a - from, b - from};
		if(d[idx] == ans) {
			s.insert(i);
		}
		if(d[idx] < ans) {
			less_cnt++;
		}
		if(d[idx] > ans) {
			more_cnt++;
		}
	}
	if(less_cnt > n / 2 || more_cnt > n / 2) {
		return -ans;
	}
	vector<int> di(1 + n, 0);
	for(int i : s) {
		int a = dist(i, X);
		int b = dist(i, Y);
		int from = (a + b - diam) / 2;
		di[i] = from;
	}
	for(int i : s) {
		for(int j : s) {
			int dij = dist(i, j);
			int cnt = 0;
			if(dij < di[i] + di[j]) {
				cnt++;
			}
			if(cnt > n / 2) {
				return -ans;
			}
		}
	}
	return ans;
}

Compilation message (stderr)

towns.cpp: In function 'int hubDistance(int, int)':
towns.cpp:25:28: warning: unused parameter 'sub' [-Wunused-parameter]
   25 | 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