Submission #548888

#	Time	Username	Problem	Language	Result	Execution time	Memory
548888		CSQ31	Friend (IOI14_friend)	C++17	11 / 100	23 ms	4500 KiB

friend

#include "friend.h"
#include<bits/stdc++.h>
using namespace std;
typedef long long int ll;
typedef vector<vector<int>> vii;
#define pb push_back
#define sz(a) (int)(a.size())
struct FlowEdge {
    int v, u;
    long long cap, flow = 0;
    FlowEdge(int v, int u, long long cap) : v(v), u(u), cap(cap) {}
};

struct Dinic {
    const long long flow_inf = 1e18;
    vector<FlowEdge> edges;
    vector<vector<int>> adj;
    int n, m = 0;
    int s, t;
    vector<int> level, ptr;
    queue<int> q;

    Dinic(int n, int s, int t) : n(n), s(s), t(t) {
        adj.resize(n);
        level.resize(n);
        ptr.resize(n);
    }

    void add_edge(int v, int u, long long cap) {
        edges.emplace_back(v, u, cap);
        edges.emplace_back(u, v, 0);
        adj[v].push_back(m);
        adj[u].push_back(m + 1);
        m += 2;
    }

    bool bfs() {
        while (!q.empty()) {
            int v = q.front();
            q.pop();
            for (int id : adj[v]) {
                if (edges[id].cap - edges[id].flow < 1)
                    continue;
                if (level[edges[id].u] != -1)
                    continue;
                level[edges[id].u] = level[v] + 1;
                q.push(edges[id].u);
            }
        }
        return level[t] != -1;
    }

    long long dfs(int v, long long pushed) {
        if (pushed == 0)
            return 0;
        if (v == t)
            return pushed;
        for (int& cid = ptr[v]; cid < (int)adj[v].size(); cid++) {
            int id = adj[v][cid];
            int u = edges[id].u;
            if (level[v] + 1 != level[u] || edges[id].cap - edges[id].flow < 1)
                continue;
            long long tr = dfs(u, min(pushed, edges[id].cap - edges[id].flow));
            if (tr == 0)
                continue;
            edges[id].flow += tr;
            edges[id ^ 1].flow -= tr;
            return tr;
        }
        return 0;
    }

    long long flow() {
        long long f = 0;
        while (true) {
            fill(level.begin(), level.end(), -1);
            level[s] = 0;
            q.push(s);
            if (!bfs())
                break;
            fill(ptr.begin(), ptr.end(), 0);
            while (long long pushed = dfs(s, flow_inf)) {
                f += pushed;
            }
        }
        return f;
    }
};
int e[1000][1000],c[1000],N;
bool vis[1000];
bool check =1;
void dfs(int v){
	vis[v] = 1;
	for(int i=0;i<N;i++){
		if(e[v][i] && !vis[i]){
			c[i] = c[v]^1;
			dfs(i);
		}
		if(e[v][i] && vis[i] && c[i] == c[v])check = 0;
	}
	
}
int findSample(int n,int confidence[],int h[],int protocol[]){
	N=n;
	int ans = 0;
	bool sub4 = 1;
	for(int i=1;i<n;i++){
		if(protocol[i] == 2)sub4 = 0;
	}
	if(n<=10){
		vector<set<int>>adj(n);
		for(int i=1;i<n;i++){
			if(!protocol[i]){
				adj[i].insert(h[i]);
				adj[h[i]].insert(i);
			}else{
				for(int x:adj[h[i]]){
					adj[i].insert(x);
					adj[x].insert(i);
				}
			}
			if(protocol[i] == 2){
				adj[i].insert(h[i]);
				adj[h[i]].insert(i);
			}
		}
		for(int i=0;i<(1<<n);i++){
			vector<int>v;
			int cost = 0;
			for(int j=0;j<n;j++){
				if(i&(1<<j)){
					v.push_back(j);
					cost+=confidence[j];
				}
			}
			for(int x:v){
				for(int y:v){
					if(adj[x].count(y) || adj[y].count(x))cost = 0;
				}
			}
			ans = max(ans,cost);
		}
		return ans;
	}
	if(sub4){
		for(int i=1;i<n;i++){
			if(!protocol[i])e[i][h[i]] = e[h[i]][i] = 1;
			else{
				for(int j=0;j<n;j++){
					if(e[h[i]][j])e[i][j] = e[j][i] = 1;
				}
			}
		}
		Dinic d(2*n+2,2*n,2*n+1);
		for(int i=0;i<n;i++){
			if(!vis[i])dfs(i);
		}
		assert(check);
		int ans = 0;
		for(int i=0;i<n;i++){
			int cnt = 0;
			for(int j=0;j<n;j++)cnt+=e[i][j];
			if(!cnt){
				ans++;
				continue;
			}
			if(!c[i]){
				d.add_edge(2*n,i,1);
				for(int j=0;j<n;j++){
					if(e[i][j])d.add_edge(i,n+j,1);
				}
			}
			else d.add_edge(n+i,2*n+1,1);
		}
		ans+=d.flow();
		return ans;
	}
	return 0;
}

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