Submission #922032

#	Time	Username	Problem	Language	Result	Execution time	Memory
922032		Macker	Friend (IOI14_friend)	C++14	46 / 100	140 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()

vector<vector<int>> adj;
vector<vector<int>> blocked;
vector<vector<int>> flows;
vector<int> h;
vector<vector<int>::iterator> idx;
int n;

bool fdfs(int a, int t){
	if(a == t) return 1;
	for(; idx[a] != adj[a].end(); idx[a]++){
		int b = *idx[a];
		if(h[b] == h[a] + 1 && blocked[a][b] < flows[a][b]){
			if(fdfs(b, t)){
				blocked[a][b]++;
				blocked[b][a]--;
				return 1;
			}
		}
	}
	return 0;
}

bool bfs(int s, int t){
	queue<int> q({s});
	h[s] = 0;
	bool ret = 0;
	while(q.size()){
		int a = q.front(); q.pop();
		idx[a] = adj[a].begin();
		for (auto &b : adj[a]) {
			if(h[b] == -1 && blocked[a][b] < flows[a][b]){
				h[b] = h[a] + 1;
				q.push(b);
				if(b == t) ret = 1;
			}
		}
	}
	return ret;
}

int flow(int s, int t){
	h.assign(n, -1);
	int res = 0;
	while(bfs(s, t)){
		int f;
		while(fdfs(s, t)) res++;
		h.assign(n, -1);
	}
	return res;
}

// Find out best sample
int findSample(int N,int confidence[],int host[],int protocol[]){
	n = N;
	bool no0 = 1, no1 = 1, no2 = 1, ones = 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;
		if(confidence[i] > 1) ones = false;
	}

	adj.resize(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;
	}
	if(ones && no2){

		vector<int> vis(n);
		vector<int> lef, rig;
		n += 2;
		adj.resize(n);
		blocked.resize(n, vector<int>(n));
		flows.resize(n, vector<int>(n));
		idx.resize(n);
		function<void(int, bool)> dfs = [&](int a, bool l){
			vis[a] = true;
			if(l) lef.push_back(a);
			else rig.push_back(a);
			for (auto &b : adj[a]) {
				if(!vis[b]) dfs(b, !l);
			}
		};
		dfs(0, 0);
		for (auto &i : lef) {
			for (auto &j : adj[i]) {
				flows[i][j] = 1;
			}
			adj[n - 2].push_back(i);
			adj[i].push_back(n - 2);
			flows[n - 2][i] = 1;
		}
		for (auto &i : rig) {
			adj[n - 1].push_back(i);
			adj[i].push_back(n - 1);
			flows[i][n - 1] = 1;
		}

		int x = flow(n - 2, n - 1);
		return rig.size() - x + lef.size();
	}
}

Compilation message (stderr)

friend.cpp: In function 'int flow(int, int)':
friend.cpp:52:7: warning: unused variable 'f' [-Wunused-variable]
   52 |   int f;
      |       ^
friend.cpp: In function 'int findSample(int, int*, int*, int*)':
friend.cpp:171:1: warning: control reaches end of non-void function [-Wreturn-type]
  171 | }
      | ^

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