Submission #295672

#	Time	Username	Problem	Language	Result	Execution time	Memory
295672		stoyan_malinin	Friend (IOI14_friend)	C++14	0 / 100	6 ms	512 KiB

friend

#include "friend.h"
//#include "grader.cpp"

#include <queue>
#include <vector>
#include <cstring>
#include <iostream>

using namespace std;

const int MAXN = 1015;

int n;
vector <int> graph[MAXN];

void constructGrahp(int n, int confidence[], int host[], int protocol[])
{
    for(int x = 1;x<=n;x++)
    {
        if(protocol[x]==0)
        {
            graph[ host[x] ].push_back(x);
            graph[x].push_back(host[x]);
        }
        else if(protocol[x]==1)
        {
            for(int y: graph[ host[x] ])
            {
                graph[y].push_back(x);
                graph[x].push_back(y);
            }
        }
        else if(protocol[x]==2)
        {
            graph[x].push_back(host[x]);
            graph[ host[x] ].push_back(x);

            for(int y: graph[ host[x] ])
            {
                graph[y].push_back(x);
                graph[x].push_back(y);
            }
        }
    }
}

namespace Subtask1
{
    bool can(int x, int mask)
    {
        for(int y: graph[x])
        {
            if(((mask>>y)&1)==1) return false;
        }

        return true;
    }

    int rec(int x, int mask, int confidence[])
    {
        if(x==n) return 0;

        int answer = rec(x+1, mask, confidence);
        if(can(x, mask)==true) answer = max(answer, confidence[x]+rec(x+1, (mask|(1<<x)), confidence));

        return answer;
    }

    int solve(int n, int confidence[], int host[], int protocol[])
    {
        constructGrahp(n, confidence, host, protocol);
        return rec(0, 0, confidence);
    }
};

namespace Subtask2
{
    int solve(int n, int confidence[], int host[], int protocol[])
    {
        int ans = 0;
        for(int x = 0;x<n;x++) ans += confidence[x];

        return ans;
    }
};

namespace Subtask3
{
    int solve(int n, int confidence[], int host[], int protocol[])
    {
        int ans = 0;
        for(int x = 0;x<n;x++) ans = max(ans, confidence[x]);

        return ans;
    }
};

namespace Subtask4
{
    int memo[MAXN][2];

    int rec(int x, int last, bool take, int confidence[])
    {
        if(memo[x][take]!=-1)
            return memo[x][take];

        int answer = 0;
        if(take==true)
        {
            answer += confidence[x];
            for(int y: graph[x])
            {
                if(y==last) continue;
                answer += rec(y, x, false, confidence);
            }
        }
        else
        {
            for(int y: graph[x])
            {
                if(y==last) continue;
                answer += max(rec(y, x, true, confidence), rec(y, x, false, confidence));
            }
        }

        memo[x][take] = answer;
        return answer;
    }

    int solve(int n, int confidence[], int host[], int protocol[])
    {
        memset(memo, -1, sizeof(memo));
        constructGrahp(n, confidence, host, protocol);

        return max(rec(0, -1, false,  confidence), rec(0, -1, true, confidence));
    }
};

namespace Subtask5
{
    struct MaxFlowGraph
    {
        int S, T;

        int dist[MAXN], ind[MAXN];

        vector <int> edges;
        vector <pair <int, int>> graph[MAXN];

        MaxFlowGraph(){}
        MaxFlowGraph(int S, int T)
        {
            this->S = S;
            this->T = T;
        }

        void addEdge(int u, int v, int cap)
        {
            graph[u].push_back({v, edges.size()});
            edges.push_back(cap);

            graph[v].push_back({u, edges.size()});
            edges.push_back(cap);
        }

        void bfs(int x)
        {
            memset(dist, -1, sizeof(dist));
            queue <int> q;

            dist[x] = 0;
            q.push(x);

            while(q.empty()==false)
            {
                x = q.front();
                q.pop();

                for(pair <int, int> y: graph[x])
                {
                    if(dist[y.first]==-1 && edges[y.second]>0)
                    {
                        dist[y.first] = dist[x] + 1;
                        q.push(y.first);
                    }
                }
            }
        }

        int dfs(int x, int minEdge)
        {
            if(x==T) return minEdge;
            //cout << " ==> " << x << '\n';

            for(int i = ind[x];i<graph[x].size();i++)
            {
                if(dist[ graph[x][i].first ]==dist[x]+1 && edges[ graph[x][i].second ]>0)
                {
                    int flow = dfs(graph[x][i].first, min(minEdge, edges[ graph[x][i].second ]));
                    if(flow!=-1)
                    {
                        edges[ graph[x][i].second ] -= flow;
                        edges[ graph[x][i].second^1 ] += flow;

                        return flow;
                    }
                }

                //ind[x]++;
            }

            return -1;
        }

        int Dinic()
        {
            int flow = 0;

            while(true)
            {
                //cout << " ----- " << '\n';

                bfs(S);
                if(dist[T]==-1) break;

                memset(ind, 0, sizeof(ind));
                while(true)
                {
                    int add = dfs(S, 1);
                    if(add==-1) break;

                    flow += add;
                }
            }

            return flow;
        }
    };

    int color[MAXN];
    void dfsColor(int x, int col, MaxFlowGraph &G)
    {
        color[x] = col + 1;
        for(pair <int, int> y: G.graph[x])
        {
            if(color[y.first]==0)
            {
                dfsColor(y.first, col^1, G);
            }
        }
    }

    int solve(int n, int confidence[], int host[], int protocol[])
    {
        int S = n, T = n + 1;
        MaxFlowGraph G(S, T);

        for(int x = 1;x<n;x++)
        {
            if(protocol[x]==0)
            {
                G.addEdge(host[x], x, 1);
            }
            else
            {
                for(pair <int, int> y: G.graph[ host[x] ])
                {
                    G.addEdge(y.first, x, 1);
                }
            }
        }

        for(int x = 0;x<n;x++)
        {
            if(color[x]==0) dfsColor(x, 0, G);
        }

        for(int x = 0;x<n;x++)
        {
            if(color[x]==1) G.addEdge(S, x, 1);
            else G.addEdge(x, T, 1);
        }

        //cout << "K" << '\n';
        return n - G.Dinic();
    }
};

int guessSubtask(int n, int confidence[], int host[], int protocol[])
{
    if(n<=10) return 1;

    bool subtask2 = true;
    for(int x = 1;x<n;x++)
    {
        if(protocol[x]!=1)
        {
            subtask2 = false;
            break;
        }
    }
    if(subtask2==true) return 2;

    bool subtask3 = true;
    for(int x = 1;x<n;x++)
    {
        if(protocol[x]!=2)
        {
            subtask3 = false;
            break;
        }
    }
    if(subtask3==true) return 3;

    bool subtask4 = true;
    for(int x = 1;x<n;x++)
    {
        if(protocol[x]!=0)
        {
            subtask4 = false;
            break;
        }
    }
    if(subtask4==true) return 4;

    bool subtask5 = true;
    for(int x = 1;x<n;x++)
    {
        if(protocol[x]==2)
        {
            subtask5 = false;
            break;
        }
    }
    if(subtask5==true) return 5;

    return -1;
}

int findSample(int _n,int confidence[],int host[],int protocol[])
{
    n = _n;

    int subtask = 5;//guessSubtask(n, confidence, host, protocol);
    if(subtask==2) return Subtask2::solve(n, confidence, host, protocol);
    if(subtask==3) return Subtask3::solve(n, confidence, host, protocol);

    if(subtask==1) return Subtask1::solve(n, confidence, host, protocol);
    if(subtask==4) return Subtask4::solve(n, confidence, host, protocol);
    if(subtask==5) return Subtask5::solve(n, confidence, host, protocol);

    return 0;
}

Compilation message (stderr)

friend.cpp: In member function 'int Subtask5::MaxFlowGraph::dfs(int, int)':
friend.cpp:195:33: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  195 |             for(int i = ind[x];i<graph[x].size();i++)
      |                                ~^~~~~~~~~~~~~~~~

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