Submission #922021

#	Time	Username	Problem	Language	Result	Execution time	Memory
922021		Macker	Friend (IOI14_friend)	C++14	46 / 100	135 ms	65536 KiB

friend

#include "friend.h"
#include <bits/stdc++.h>

using namespace std;
typedef long long ll;
#define all(v) v.begin(), v.end()
// Find out best sample
int findSample(int n,int confidence[],int host[],int protocol[]){
	bool no0 = 1, no1 = 1, no2 = 1;
	for (int i = 1; i < n; i++) {
		if(protocol[i] == 0) no0 = false;
		if(protocol[i] == 1) no1 = false;
		if(protocol[i] == 2) no2 = false;
	}

	vector<vector<int>> adj(n);
	for (int i = 1; i < n; i++) {
		if(protocol[i] == 1 || protocol[i] == 2){
			for (auto &j : adj[host[i]]) {
				adj[i].push_back(j);
				adj[j].push_back(i);
			}
		}
		if(protocol[i] == 0 || protocol[i] == 2) {
			adj[i].push_back(host[i]);
			adj[host[i]].push_back(i);
		}
	}
	

	if(no0 && no2){ // no edges
		int res = 0;
		for (int i = 0; i < n; i++) {
			res += confidence[i];
		}
		return res;
	}
	if(no0 && no1){ // fully conected
		int res = 0;
		for (int i = 0; i < n; i++) {
			res = max(res, confidence[i]);
		}
		return res;
	}
	if(no1 && no2){ // tree
		vector<int> odp(n, 0);
		vector<int> ndp(n, 0);

		function<void(int, int)> dfs = [&](int a, int p){
			odp[a] = confidence[a];
			for (auto &b : adj[a]) {
				if(b == p) continue;
				dfs(b, a);
				ndp[a] += max(odp[b], ndp[b]);
				odp[a] += ndp[b];
			}
		};
		dfs(0, 0);
		return max(odp[0], ndp[0]);
	}
	if(n <= 15){ // brute force
		int mx = 0;
		for (int i = 0; i < (1 << n); i++) {
			vector<bool> active(n, 0);
			int res = 0;
			bool bad = 0;
			for (int j = 0; j < n; j++) {
				if(i & (1 << j)){
					active[j] = 1;
					res += confidence[j];
				}
			}
			for (int j = 0; j < n; j++) {
				for (auto &k : adj[j]) {
					if(active[j] && active[k]) bad = 1;
				}
			}
			if(!bad) mx = max(mx, res);
		}
		return mx;
	}
	return -1;
}

• Subtask 1: 11 / 11
• Subtask 2: 8 / 8
• Subtask 3: 8 / 8
• Subtask 4: 19 / 19
• Subtask 5: 0 / 23
• Subtask 6: 0 / 31