Submission #295713

#	Time	Username	Problem	Language	Result	Execution time	Memory
295713		stoyan_malinin	Friend (IOI14_friend)	C++14	69 / 100	39 ms	2808 KiB

friend

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

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

using namespace std;

const int MAXN = 2015;

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 Edge
    {
        int u, v, val;

        Edge(){}
        Edge(int u, int v, int val)
        {
            this->u = u;
            this->v = v;
            this->val = val;
        }
    };

    struct MaxFlowGraph
    {
        int dist[MAXN];
        int startInd[MAXN];

        vector <Edge> edges;
        vector <int> graph[MAXN];

        MaxFlowGraph(){}

        void addEdge(int u, int v, int val)
        {
            //cout << u << " " << v << '\n';

            edges.push_back(Edge(u, v, val));
            edges.push_back(Edge(v, u, 0));

            graph[u].push_back(edges.size()-2);
            graph[v].push_back(edges.size()-1);
        }

        void BFS(int x)
        {
            queue <int> q;
            memset(dist, 0, sizeof(dist));

            q.push(x);
            dist[x] = 1;
            while(q.empty()==false)
            {
                x = q.front();
                q.pop();

                for(int ind: graph[x])
                {
                    Edge e = edges[ind];
                    if(dist[e.v]==0 && e.val>0)
                    {
                        q.push(e.v);
                        dist[e.v] = dist[x] + 1;
                    }
                }
            }
        }

        int DFS(int x, int minVal, int sink)
        {
            if(x==sink) return minVal;

            for(int i = startInd[x];i<int(graph[x].size());i++)
            {
                Edge e = edges[ graph[x][i] ];
                if(e.val>0 && dist[e.v]==dist[x]+1)
                {
                    int flow = DFS(e.v, min(minVal, e.val), sink);
                    if(flow!=0)
                    {
                        edges[ graph[x][i] ] .val -= flow;
                        edges[ graph[x][i]^1 ].val += flow;

                        return flow;
                    }
                }

                startInd[x]++;
            }
            return 0;
        }

        int calcFlow(int source, int sink)
        {
            int maxFlow = 0;
            while(true)
            {
                BFS(source);
                if(dist[sink]==0) break;

                while(true)
                {
                    int flow = DFS(source, MAXN, sink);
                    if(flow==0) break;

                    maxFlow += flow;
                }

                memset(startInd, 0, sizeof(startInd));
            }

            return maxFlow;
        }
    };

    int color[MAXN];
    void dfsColor(int x, int col)
    {
        color[x] = col + 1;
        for(int y: graph[x])
        {
            if(color[y]==0)
            {
                dfsColor(y, col^1);
            }
        }
    }

    int solve(int n, int confidence[], int host[], int protocol[])
    {
        int S = n + 1, T = n + 2;
        MaxFlowGraph G;

        vector <pair <int, int>> all;
        for(int x = 1;x<n;x++)
        {
            if(protocol[x]==0)
            {
                all.push_back({host[x], x});

                graph[x].push_back(host[x]);
                graph[ host[x] ].push_back(x);
                //G.addEdge(host[x], x, 1);
            }
            else
            {
                for(int y: graph[ host[x] ])
                {
                    all.push_back({y, x});

                    graph[x].push_back(y);
                    graph[y].push_back(x);
                    //G.addEdge(y.first, x, 1);
                }
            }
        }

        memset(color, 0, sizeof(color));
        for(int x = 0;x<n;x++)
        {
            if(color[x]==0) dfsColor(x, 0);
        }
        for(pair <int, int> x: all)
        {
            int u = x.first;
            int v = x.second;
            if(color[u]>color[v]) swap(u, v);

            G.addEdge(u, v, 1);
        }

        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.calcFlow(S, T);
    }
};

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 = 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;
}

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