Report problem solving: luogu P2015

Tomorrow on the exam, but the tree \ (dp \) or not.
Topic link: P2015 Binary apple tree
is actually this title double experience of it.
Dynamic transfer equation is
\ [f [i] [j ] = max (f [i] [j], f [i] [ik-1] + f [i_ {son}] [k] + e [i]. W) \]
where \ (f [i] [j ] \) representative of the in \ (I \) lawfully in the subtree rooted at \ (J \) a maximum value of a remaining branches.

\(Code\):

#include<cmath>
#include<cstdio> 
#include<iostream>
const int MAXN=105;
using namespace std;
typedef long long ll;
ll f[MAXN][MAXN],c;
int n,s,l,r,root,tot[MAXN];
struct node
{
    int to,nxt;
    ll w;
}e[MAXN<<1];
int head[MAXN],cnt=0;
int deg[MAXN];
void add(int u,int v,ll c)
{
    e[++cnt].to=v;
    e[cnt].nxt=head[u];
    e[cnt].w=c;
    head[u]=cnt;
}
int dfs(int cur,int fa)
{
    tot[cur]=0;
    for(int i=head[cur];i;i=e[i].nxt)
    {
        int j=e[i].to;
        if(j==fa) continue;
        int son=dfs(j,cur)+1;
        tot[cur]+=son;
        for(int k=tot[cur];k>=0;k--)
        {
            for(int v=0;k-v-1>=0&&v<=son;v++) f[cur][k]=max(f[cur][k],f[cur][k-v-1]+f[j][v]+e[i].w);
        }
    }
    return tot[cur];
}
int main()
{
    scanf("%d%d",&n,&s);
    for(int i=1;i<n;i++)
    {
        scanf("%d%d%lld",&l,&r,&c);
        add(l,r,c);
        add(r,l,c);
        deg[l]++,deg[r]++;
    }
    for(int i=1;i<=n;i++) if(deg[i]==2) root=i;
    dfs(root,0);
    printf("%lld\n",f[root][s]);
    return 0;
}

If that tree backpack of it.