Submission #1018040

#	Time	Username	Problem	Language	Result	Execution time	Memory
1018040		serkanrashid	Friend (IOI14_friend)	C++14	19 / 100	24 ms	4444 KiB

friend

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

using namespace std;

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;
    }
};

const int maxn = 1024;

vector<int>g[maxn];
int con[maxn],used[maxn];
vector<int>team[3];

void dfs(int beg)
{
    for(int nb : g[beg])
    {
        if(used[nb]) continue;
        used[nb] = 3-used[beg];
        team[used[nb]].push_back(nb);
        dfs(nb);
    }
}

int findSample(int n, int confidence[], int host[], int protocol[])
{
    for(int i = 0; i < n; i++) con[i] = confidence[i];

    bool f3 = true;
    for(int i = 1; i < n; i++)
    {
        if(protocol[i]!=2) f3 = false;
        if(protocol[i]==0)
        {
            g[host[i]].push_back(i);
            g[i].push_back(host[i]);
        }
        if(protocol[i]==1)
        {
            for(int nb : g[host[i]])
            {
                g[nb].push_back(i);
                g[i].push_back(nb);
            }
        }
        if(protocol[i]==2)
        {
            for(int nb : g[host[i]])
            {
                g[nb].push_back(i);
                g[i].push_back(nb);
            }
            g[host[i]].push_back(i);
            g[i].push_back(host[i]);
        }
    }

    ///SUBTASKS
    if(f3)
    {
        int ans = 0;
        for(int i = 0; i < n; i++) if(con[i]>ans) ans = con[i];
        return ans;
    }
    if(n<=10)
    {
        int ans = 0;
        for(int mask = 1; mask < (1<<n); mask++)
        {
            int ch = 0;
            for(int j = 0; j < n; j++) if(mask&(1<<j)) ch += confidence[j];
            bool f = true;
            for(int j = 0; j < n; j++)
            {
                if((mask&(1<<j))==0) continue;
                for(int nb : g[j]) if(mask&(1<<nb)) f = false;
            }
            if(f) ans = max(ans,ch);
        }
        return ans;
    }


    long long inf = 1e18;

    for(int i = 0; i < n; i++)
    {
        if(used[i]) continue;
        team[1].push_back(i);
        used[i] = 1;
        dfs(i);
    }
    Dinic patok(n+2,n,n+1);
    for(int red : team[1])
    {
        patok.add_edge(n,red,1);
        for(int blue : g[red]) patok.add_edge(red,blue,inf);
    }
    for(int blue : team[2]) patok.add_edge(blue,n+1,1);
    return patok.flow();
}

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