Submission #1018051

#	Time	Username	Problem	Language	Result	Execution time	Memory
1018051		serkanrashid	Friend (IOI14_friend)	C++14	38 / 100	17 ms	4584 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 s,t,n,m = 0;
    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 <= 0) 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 < 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 <= 0) 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;
            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];



int dp[maxn][2];

void dfs(int beg, int par)
{
    dp[beg][0] = dp[beg][1] = 0;

    int sum[2] = {0,0};
    for(int nb : g[beg])
    {
        if(nb==par) continue;
        dfs(nb,beg);
        sum[0] += dp[nb][0];
        sum[1] += dp[nb][1];
    }
    dp[beg][0] = sum[1];
    dp[beg][1] = max(dp[beg][0] , sum[0] + con[beg]);
}

int used[maxn];
vector<int>team[3];

void dfs_color(int beg)
{
    for(int nb : g[beg])
    {
        if(used[nb]) continue;
        used[nb] = 3-used[beg];
        team[used[nb]].push_back(nb);
        dfs_color(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;
    bool f24 = true;
    for(int i = 1; i < n; i++)
    {
        if(i>1 && protocol[i-1] != protocol[i]) f24 = false;
        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(f24)
    {
        dfs(0,0);
        return max(dp[0][0],dp[0][1]);
    }

    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_color(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 n-patok.flow();
}

Compilation message (stderr)

friend.cpp: In constructor 'Dinic::Dinic(int, int, int)':
friend.cpp:19:13: warning: 'Dinic::n' will be initialized after [-Wreorder]
   19 |     int s,t,n,m = 0;
      |             ^
friend.cpp:19:9: warning:   'int Dinic::s' [-Wreorder]
   19 |     int s,t,n,m = 0;
      |         ^
friend.cpp:23:5: warning:   when initialized here [-Wreorder]
   23 |     Dinic(int n, int s, int t) : n(n), s(s), t(t)
      |     ^~~~~
friend.cpp: In member function 'long long int Dinic::dfs(int, long long int)':
friend.cpp:61:35: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   61 |         for(int &cid = ptr[v];cid < adj[v].size(); cid++)
      |                               ~~~~^~~~~~~~~~~~~~~

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