Submission #1220773

#	Time	Username	Problem	Language	Result	Execution time	Memory
1220773		HappyCapybara	Towns (IOI15_towns)	C++20	39 / 100	10 ms	328 KiB

towns

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

map<pair<int,int>,int> res;

int getDist(int a, int b){
	if (a == b) return 0;
	if (a > b) swap(a, b);
	if (res.find({a, b}) == res.end()) res[{a, b}] = getDistance(a, b);
	return res[{a, b}];
}

int hubDistance(int N, int sub){
	res.clear();
	vector<int> d1(N, 0), d2(N, 0);
	int bsf = 0, f1, f2;
	for (int i=1; i<N; i++){
		int d = getDist(0, i);
		if (d > bsf){
			bsf = d;
			f1 = i;
		}
	}
	bsf = 0;
	for (int i=0; i<N; i++){
		if (i == f1) continue;
		int d = getDist(f1, i);
		d1[i] = d;
		if (d > bsf){
			bsf = d;
			f2 = i;
		}
	}
	int R = pow(10, 9);
	map<int,vector<int>> m;
	for (int i=0; i<N; i++){
		if (i == f1 || i == f2) continue;
		int d = getDist(f2, i);
		d2[i] = d;
		int l = (d1[i]+d2[i]-bsf)/2;
		R = min(R, max(d1[i], d2[i])-l);
		m[d1[i]-l].push_back(i);
	}
	//cout << bsf << endl;
	bool bal = false;
	//for (auto it=m.begin(); it != m.end(); it++) cout << it->first << " " << it->second.size() << endl;
	for (auto it=m.begin(); it != m.end(); it++){
		if (it->first == R || it->first == bsf-R){
			int x1 = 1, x2 = 0, x3 = 1;
			for (auto jt=m.begin(); jt != it; jt++) x1 += jt->second.size();
			for (auto jt=next(it); jt != m.end(); jt++) x3 += jt->second.size();
			/*for (int v : it->second){
				int cur = 0;
				for (int w : it->second){
					if (d1[v]+d1[w]-getDist(v, w) > 2*it->first) cur++;		
				}
				x2 = max(x2, cur);
			}*/
			vector<int> l1, l2;
			for (int v : it->second){
				if (l1.empty()) l1.push_back(v);
				if (d1[v]+d1[l1.back()]-getDist(v, l1.back()) > 2*it->first) l2.push_back(v);
				else {
					l1.push_back(v);
					if (!l2.empty()){
						l1.push_back(l2.back());
						l2.pop_back();
					}
				}
			}
			for (int v : it->second){
				if (d1[v]+d1[l1.back()]-getDist(v, l1.back()) > 2*it->first) x2++;
			}
			//cout << x1 << " " << x2 << " " << x3 << endl;
			if (x1 <= N/2 && x2 <= N/2 && x3 <= N/2) bal = true;
		}
	}
	if (bal) return R;
	else return -R;
}

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