Submission #34731

#	Time	Username	Problem	Language	Result	Execution time	Memory
34731		oOZinzOo	Beads and wires (APIO14_beads)	C++11	100 / 100	315 ms	24940 KiB

beads

#include<cstdio>
#include<algorithm>
#include<vector>
#include<cstring>
using namespace std;
int alln;
vector <pair<int,int> > E[200005];

int dp[200005][2][2][2];

int recur(int u,int ins,int wp,int can10,int pre){
    if(dp[u][ins][wp][can10] >= 0)
        return dp[u][ins][wp][can10];
    //printf("--> dp infor %d %d %d %d %d\n",u,ins,wp,can10,pre);
    if(E[u].size() <= 1)
        return dp[u][ins][wp][can10] = 0;
    if(ins == 1){
        if(wp == 0 && E[u].size() <= 2  )
            return dp[u][ins][wp][can10] = 0;
        else if(wp == 1 && E[u].size() <= 1)
            return dp[u][ins][wp][can10] = 0;
    }
    int sum = 0;
    for(int i=0;i<E[u].size();++i){
        int v = E[u][i].first;
        if(v == pre)
            continue;
        int w = E[u][i].second;
        sum += max( recur(v,0,0,0,u) ,  recur(v,1,1,0,u)+w*(E[v].size() > 1) ) ;
    }

    pair<int,int> t101,t102,f101,f102;
    t101 = t102 = f101 = f102 = {0,0};

    for(int i=0;i<E[u].size();++i){
        int v = E[u][i].first;
        if(v == pre)
            continue;
        int w = E[u][i].second;
        if(can10 == true){
            if(ins == 0){
                int del = max( recur(v,0,0,0,u) ,  recur(v,1,1,0,u)+w*(E[v].size() > 1) );
                int add = max( recur(v,0,0,can10,u) , max( recur(v,1,0,can10,u) , recur(v,1,1,can10,u)+w*(E[v].size() > 1) ) );
                pair<int,int> tmp = { sum-del+add , v };
                if(t101.first < tmp.first)
                    t102 = t101 , t101 = tmp;
                else if(t102.first < tmp.first)
                    t102 = tmp;
            }
            else{
                int del = max( recur(v,0,0,0,u) ,  recur(v,1,1,0,u)+w*(E[v].size() > 1) );
                int add = max( recur(v,0,0,can10,u) , recur(v,1,0,can10,u) )+w;
                //printf("-->1 uv %d %d val %d\n",u,v,sum-del+add);
                pair<int,int> tmp = { sum-del+add , v };
                if(t101.first < tmp.first)
                    t102 = t101 , t101 = tmp;
                else if(t102.first < tmp.first)
                    t102 = tmp;
                //printf("--> %d %d\n",t101.first , t102.first);
            }
        }
        if(ins == 0){
            int del = max( recur(v,0,0,0,u) ,  recur(v,1,1,0,u)+w*(E[v].size() > 1) );
            int add = max( recur(v,0,0,0,u) , recur(v,1,1,0,u)+w*(E[v].size() > 1)  );
            pair<int,int> tmp = { sum-del+add , v };
            if(f101.first < tmp.first)
                f102 = t101 , f101 = tmp;
            else if(f102.first < tmp.first)
                f102 = tmp;
        }
        else{
            int del = max( recur(v,0,0,0,u) ,  recur(v,1,1,0,u)+w*(E[v].size() > 1) );
            int add = recur(v,0,0,0,u) + w;
            //printf("-->0 uv %d %d val %d\n\n",u,v,sum-del+add);
            pair<int,int> tmp = { sum-del+add , v };
            if(f101.first < tmp.first)
                f102 = f101 , f101 = tmp;
            else if(f102.first < tmp.first)
                f102 = tmp;
            //printf("--> %d %d\n",f101.first , f102.first);
        }
    }

    if(ins == 0)
        return dp[u][ins][wp][can10] = max( t101.first , f101.first );
    if(can10){
        if(wp)
            return dp[u][ins][wp][can10] = t101.first;
        if(t101.second != f101.second)
            return dp[u][ins][wp][can10] = t101.first + f101.first -sum;
        //printf("*** %d %d\n",t101.first+f102.first , t102.first+f101.first);
        return dp[u][ins][wp][can10] = max(t101.first+f102.first , t102.first+f101.first)-sum;
    }
    else{
        if(wp)
            return dp[u][ins][wp][can10] = f101.first;
        return dp[u][ins][wp][can10] = f101.first+f102.first - sum;
    }

}

int main()
{
    memset(dp,-1,sizeof(dp));
    scanf("%d",&alln);
    for(int i=1;i<alln;++i){
        int u,v;
        int w;
        scanf("%d%d%d",&u,&v,&w);
        E[u].push_back({v,w});
        E[v].push_back({u,w});
    }
    int root = 1;
    E[root].push_back({0,0});
    printf("%d\n",max( recur(root,0,0,1,0) , recur(root,1,0,1,0) ) );
    //printf("--> %d\n",recur(root,1,0,1,0));
    return 0;
}

/**

5
1 2 10
1 3 40
1 4 15
1 5 20

10
4 10 2
1 2 21
1 3 13
6 7 1
7 9 5
2 4 3
2 5 8
1 6 55
6 8 34

6
1 2 15
2 3 35
3 4 20
4 5 30
5 6 25


*/

Compilation message (stderr)

beads.cpp: In function 'int recur(int, int, int, int, int)':
beads.cpp:24:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i=0;i<E[u].size();++i){
                 ~^~~~~~~~~~~~
beads.cpp:35:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i=0;i<E[u].size();++i){
                 ~^~~~~~~~~~~~
beads.cpp: In function 'int main()':
beads.cpp:105:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d",&alln);
     ~~~~~^~~~~~~~~~~~
beads.cpp:109:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d%d%d",&u,&v,&w);
         ~~~~~^~~~~~~~~~~~~~~~~~~

• Subtask 1: 13 / 13
• Subtask 2: 15 / 15
• Subtask 3: 29 / 29
• Subtask 4: 43 / 43