Submission #810247

#	Time	Username	Problem	Language	Result	Execution time	Memory
810247		Kerim	Friend (IOI14_friend)	C++17	46 / 100	21 ms	4308 KiB

friend

#include "friend.h"
#include "bits/stdc++.h"
#define pb(x) push_back(x)
using namespace std;
const int N = 1005;
vector<int> adj[N];

void add_edge(int u, int v){
	adj[u].pb(v);
	adj[v].pb(u);
}

int dp[N][2];
void dfs(int nd, int pr, int val[]){
	dp[nd][1] = val[nd];
	dp[nd][0] = 0;
	for (auto c: adj[nd]){
		if (c == pr)
			continue;
		dfs(c, nd, val);
		dp[nd][1] += dp[c][0];
		dp[nd][0] += max(dp[c][0], dp[c][1]);
	}
}

int vis[N], col[N], matched[N];
void dfs0(int nd){
	vis[nd] = 1;
	for (auto to: adj[nd])
		if (!vis[to]){
			col[to] = col[nd] ^ 1;
			dfs0(to);
		}
}

bool dfs1(int nd){
	if (vis[nd])
		return 0;
	vis[nd] = 1;
	for (auto x: adj[nd]){
		if (matched[x] == -1 or dfs1(matched[x])){
			matched[x] = nd;
			return 1;
		}
	}
	return 0;
}
int findSample(int n,int arr[],int host[],int protocol[]){
	for (int i = 0; i < n; i++)
		adj[i].clear();
	bool subtask1 = (n <= 10);
	bool subtask2 = true, subtask3 = true;
	bool subtask4 = true, subtask5 = true;
	// Build graph
	for (int i = 1; i < n; i++){
		int v = host[i], p = protocol[i];
		subtask4 &= (p == 0);
		subtask2 &= (p == 1);
		subtask3 &= (p == 2);
		subtask5 &= (p <= 1);
		if (p == 0)//IAmYourFriend
			add_edge(v, i);
		else if(p == 1){//MyFriendsAreYourFriends
			for (auto to: adj[v])
				add_edge(to, i);
		}
		else{//WeAreYourFriends
			for (auto to: adj[v])
				add_edge(to, i);
			add_edge(v, i);
		}
	}
	int answer = 0;
	if (subtask1){
		for (int mask = 0; mask < (1<<n); mask++){
			bool bad = 0;
			int sum = 0;
			for (int i = 0; i < n; i++)
				if (mask>>i&1){
					sum += arr[i];
					for (auto to: adj[i])
						bad |= (mask>>to&1);
				}
			if (!bad)
				answer = max(answer, sum);
		}
	}
	else if(subtask2){
		for (int i = 0; i < n; i++)
			answer += arr[i];
	}
	else if (subtask3){
		for (int i = 0; i < n; i++)
			answer = max(answer, arr[i]);
	}
	else if (subtask4){
		dfs(0, -1, arr);
		answer = max(dp[0][0], dp[0][1]);
	}
	else if(subtask5){
		for (int i = 0; i < n; i++)
			vis[i] = col[i] = 0;
		dfs0(0);
		vector<int> L, R;
		for (int i = 0; i < n; i++){
			if (!col[i])
				L.pb(i);
			else	
				R.pb(i);
		}
		// Kuhn's algorithm
		for (auto x: R)
			matched[x] = -1;
		for (auto x: L){
			for (auto y: L)
				vis[y] = false;
			dfs1(x);
		}
		int MM = 0;
		for (auto x: R)
			MM += (matched[x] != -1);
		answer = n - MM; 
	}
	return answer;
}

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