Submission #120896

#	Time	Username	Problem	Language	Result	Execution time	Memory
120896		Bruteforceman	Towns (IOI15_towns)	C++11	61 / 100	25 ms	480 KiB

towns

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

map <pair <int, int>, int> mp;

int distance(int i, int j) {
	if(i == j) return 0;
	if(i > j) swap(i, j);
	if(mp.find(make_pair(i, j)) != mp.end()) return mp[make_pair(i, j)];
	return mp[make_pair(i, j)] = getDistance(i, j);
}

int hubDistance(int N, int sub) {
	mp.clear();
	int opt = 0;
	int dist = 0;
	for(int i = 1; i < N; i++) {
		int d = distance(0, i);
		if(d > dist) {
			dist = d;
			opt = i;
		}
	}
	int P = 0, Q = opt;
	dist = 0;
	for(int i = 0; i < N; i++) {
		if(i == opt) continue;
		int d = distance(opt, i);
		if(d > dist) {
			dist = d;
			P = i;
		}
	}


	map <int, int> dist_chain;
	map <int, int> pos_chain;

	int R = distance(P, Q);
	int radius_pos = -1;

	for(int i = 0; i < N; i++) {
		int lca_dist = (distance(i, P) + distance(i, Q) - distance(P, Q)) / 2;
		int p_dist = distance(i, P) - lca_dist;
		int val = max(p_dist, distance(P, Q) - p_dist);
		R = min(R, val);
		dist_chain[i] = lca_dist;
		pos_chain[i] = p_dist;
	}

	if(sub <= 2) return R;

	for(int i = 0; i < N; i++) {
		int lca_dist = (distance(i, P) + distance(i, Q) - distance(P, Q)) / 2;
		int p_dist = distance(i, P) - lca_dist;
		int val = max(p_dist, distance(P, Q) - p_dist);
		if(R == val) {
			int l = 0;
			int r = 0;
			for(int ii = 0; ii < N; ii++) {
				if(pos_chain[ii] < p_dist) ++l;
				if(pos_chain[ii] > p_dist) ++r;
		 	}
		 	if(l > (N / 2) || r > (N / 2)) continue;
		 	radius_pos = p_dist;
		}
	}
	if(radius_pos < 0) return -R;

	vector <int> unmatched;

	for(int i = 0; i < N; i++) {
		if(pos_chain[i] != radius_pos) continue;
		if(unmatched.empty()) {
			unmatched.push_back(i);
			if(sub == 4) break;
		}

		int x = i;
		int y = unmatched.back();
		int d = distance(x, y);
		int lca_dist = (distance(P, x) + distance(P, y) - distance(x, y)) / 2;
		int meet = distance(P, x) - lca_dist;
		if(meet != dist_chain[x]) {
			unmatched.push_back(x);
		} else {
			unmatched.pop_back();
		}
	}
	if(unmatched.empty()) return R;

	int piv = unmatched.back();

	int cnt = 0;
	for(int i = 0; i < N; i++) {
		if(pos_chain[i] != radius_pos) continue;
		int x = i;
		int y = piv;
		int d = distance(x, y);
		int lca_dist = (distance(P, x) + distance(P, y) - distance(x, y)) / 2;
		int meet = distance(P, x) - lca_dist;	
		if(meet != dist_chain[x]) {
			++cnt;
		}
		if(cnt > (N / 2)) return -R;
	}
	return R;
}

Compilation message (stderr)

towns.cpp: In function 'int hubDistance(int, int)':
towns.cpp:82:7: warning: unused variable 'd' [-Wunused-variable]
   int d = distance(x, y);
       ^
towns.cpp:100:7: warning: unused variable 'd' [-Wunused-variable]
   int d = distance(x, y);
       ^

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