Submission #775726

#	Time	Username	Problem	Language	Result	Execution time	Memory
775726		danikoynov	Friend (IOI14_friend)	C++14	69 / 100	24 ms	8520 KiB

friend

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

using namespace std;

// Find out best sample
const int maxn = 1010;
typedef long long ll;

vector < int > adj[maxn];
int edges[maxn][maxn];
void add_edge(int v, int u)
{
    adj[v].push_back(u);
    adj[u].push_back(v);
    edges[v][u] = edges[u][v] = 1;
}

vector < int > ord;

int used[maxn];
void bfs(int v)
{
    queue < int > q;
    used[v] = 1;
    q.push(v);
    while(!q.empty())
    {
        int cur = q.front();
        q.pop();
        ord.push_back(cur);
        for (int u : adj[cur])
        {

            if (used[u] == 0)
            {
                if (used[cur] == 1)
                    used[u] = 2;
                else
                    used[u] = 1;
                q.push(u);
            }
        }
    }
}

int con[maxn], dp[maxn][2];
void dfs(int v, int p)
{
    dp[v][1] = con[v];
    used[v] = 1;
    for (int u : adj[v])
    {
        if (u == p)
            continue;
        dfs(u, v);
        dp[v][0] += max(dp[u][0], dp[u][1]);
        dp[v][1] += dp[u][0];
    }
}

struct edge
{
    int v, u, cap;

    edge(int _v, int _u, int _cap)
    {
        v = _v;
        u = _u;
        cap = _cap;
    }
};

struct dinic
{
    vector < edge > edges;
    vector < int > levels, ptr;
    vector < vector < int > > adj;
    int n, s, t;


    dinic(){};

    dinic(int _n, int _s, int _t)
    {
        n = _n;
        s = _s;
        t = _t;
        ptr.resize(n + 1);
        adj.resize(n + 1);
        levels.resize(n + 1);
    }

    void add_edge(int v, int u, int cap)
    {
        adj[v].push_back(edges.size());
        edges.push_back(edge(v, u, cap));
        adj[u].push_back(edges.size());
        edges.push_back(edge(u, v, 0));
    }


    bool bfs()
    {
        for (int i = 0; i <= n; i ++)
            levels[i] = -1;
        queue < int > q;
        q.push(s);
        levels[s] = 0;
        while(!q.empty())
        {
            int v = q.front();
            ////cout << "step " << v << endl;
            q.pop();
            for (int idx : adj[v])
            {
                edge cur = edges[idx];
                if (cur.cap > 0)
                {
                    ///if (v == s)
                      ///  cout << cur.u << endl;
                    if (levels[cur.u] == -1)
                    {
                        levels[cur.u] = levels[v] + 1;
                        q.push(cur.u);
                    }
                }
            }
        }
        ///cout << "final " << t << " " << levels[t] << endl;
        return levels[t] != -1;
    }

    int get_flow(int v, int tr)
    {
        if (v == t)
            return tr;
        ///cout << "get flow " << v << " " << tr << endl;
        for (ptr[v]; ptr[v] < adj[v].size(); ptr[v] ++)
        {
            int idx = adj[v][ptr[v]];
            edge cur = edges[idx];
            ///cout << cur.cap << endl;
            if (cur.cap > 0 && levels[cur.u] == levels[v] + 1)
            {
                int ps = get_flow(cur.u, min(cur.cap, tr));
                if (ps != 0)
                {
                    edges[idx].cap -= ps;
                    edges[idx ^ 1].cap += ps;
                    return ps;
                }
            }
        }
        return 0;
    }

    int maxflow()
    {
        int flow = 0;
        while(bfs())
        {
            ///cout << "---------" << endl;
            ///cout << flow << endl;
            fill(ptr.begin(), ptr.end(), 0);
            int cur;
            while(cur = get_flow(s, 1e9))
            {
                flow += cur;
            }
        }
        return flow;
    }

};
int findSample(int n,int confidence[],int host[],int protocol[])
{
    bool only_my = true, only_we = true;
    int mx = 0;
    for (int i = 1; i < n; i ++)
    {
        mx = max(mx, protocol[i]);
        if (protocol[i] != 1)
            only_my = false;
        if (protocol[i] != 2)
            only_we = false;
    }
    for (int i = 0; i < n; i ++)
    {
        con[i] = confidence[i];
    }

    if (n <= 10)
    {
        for (int i = 1; i < n; i ++)
        {
            if (protocol[i] == 0)
            {
                add_edge(i, host[i]);
            }
            else if (protocol[i] == 1)
            {
                for (int u : adj[host[i]])
                    add_edge(u, i);
            }
            else
            {
                for (int u : adj[host[i]])
                    add_edge(u, i);
                add_edge(i, host[i]);
            }

        }
        int ans = 0;
        for (int mask = 0; mask < (1 << n); mask ++)
        {
            bool tf = true;
            for (int bit1 = 0; bit1 < n; bit1 ++)
                for (int bit2 = 0; bit2 < n; bit2 ++)
            {
                if ((mask & (1 << bit1)) > 0 && (mask & (1 << bit2)) > 0)
                {
                    if (edges[bit1][bit2])
                        tf = false;
                }
            }
            ///cout << mask << " : " << tf << endl;
            if (!tf)
                continue;
            int cur = 0;
            for (int i = 0; i < n; i ++)
                if ((mask & (1 << i)) > 0)
                cur += confidence[i];
            ans = max(ans, cur);
        }
        return ans;

    }
    else if (only_my)
    {

        int ans = 0;
        for (int i = 0; i < n; i ++)
            ans += confidence[i];
        return ans;
    }
    else if (only_we)
    {
        int ans = 0;
        for (int i = 0; i < n; i ++)
            ans = max(ans, confidence[i]);
        return ans;
    }
    else
    if (mx < 1)
     {
        for (int i = 1; i < n; i ++)
        {
            if (protocol[i] == 0)
            {
                add_edge(i, host[i]);
            }
            else
            {
                assert(0);
            }
            /**if (protocol[i] == 2)
            {
                for (int u : adj[host[i]])
                    add_edge(u, i);
            }*/
        }
        ll ans = 0;
        for (int i = 0; i < n; i ++)
        {
            if (!used[i])
            {
                dfs(i, -1);
                ans = ans + max(dp[i][0], dp[i][1]);
            }

        }

        return ans;
    }
    else
    {
        for (int i = 1; i < n; i ++)
        {
            if (protocol[i] == 0)
            {
                add_edge(i, host[i]);
            }
            else
            if (protocol[i] == 1)
            {
                for (int u : adj[host[i]])
                    add_edge(u, i);
            }
        }
        int ans = 0;
        for (int i = 0; i < n; i ++)
        {
            if (!used[i])
            {
                bfs(i);
            }

        }

        int s = n, t = n + 1;
        dinic dc(n + 2, n, n + 1);
        for (int i = 0; i < n; i ++)
        {
            if (used[i] == 1)
            {
                dc.add_edge(s, i, 1);
                for (int u : adj[i])
                {
                    dc.add_edge(i, u, 1);
                    ///cout << "edge " << i << " " << u << endl;
                }
            }
            else
            {
                dc.add_edge(i, t, 1);
            }
        }

        return n - dc.maxflow();
    }


}

Compilation message (stderr)

friend.cpp: In member function 'int dinic::get_flow(int, int)':
friend.cpp:139:29: warning: comparison of integer expressions of different signedness: '__gnu_cxx::__alloc_traits<std::allocator<int>, int>::value_type' {aka 'int'} and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  139 |         for (ptr[v]; ptr[v] < adj[v].size(); ptr[v] ++)
friend.cpp: In member function 'int dinic::maxflow()':
friend.cpp:167:23: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
  167 |             while(cur = get_flow(s, 1e9))
      |                   ~~~~^~~~~~~~~~~~~~~~~~
friend.cpp: In function 'int findSample(int, int*, int*, int*)':
friend.cpp:301:13: warning: unused variable 'ans' [-Wunused-variable]
  301 |         int ans = 0;
      |             ^~~

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