【Codeforces Round #419 (Div. 1)】Codeforces 815C Karen and Supermarket

#include<cstdio>
#include<cstring>
#include<vector>
#include<algorithm>
using namespace std;
const int maxn=5010,oo=0x3f3f3f3f;
vector<int> son[maxn];
int size[maxn],c[maxn],d[maxn],f[maxn][maxn],g[maxn][maxn],val[maxn],tf[maxn],tg[maxn],n,m,clo;
void dfs(int u)
{
//printf("in:%d\n",u);
int v;
for (int i=2;i<=n;i++) f[u][i]=g[u][i]=oo;
size[u]=1;
f[u][1]=c[u]-d[u];
g[u][1]=c[u];
for (vector<int>::iterator it=son[u].begin();it!=son[u].end();++it)
{
v=*it;
dfs(v);
for (int i=0;i<=size[u];i++)
{
tf[i]=f[u][i];
tg[i]=g[u][i];
}
for (int i=0;i<=size[u];i++)
for (int j=1;j<=size[v];j++)
{
g[u][i+j]=min(g[u][i+j],g[v][j]+tg[i]);
f[u][i+j]=min(f[u][i+j],i?f[v][j]+tf[i]:oo);
}
size[u]+=size[v];
}
for (int i=1;i<=size[u];i++) f[u][i]=min(f[u][i],g[u][i]);
//printf("out:%d %d\n",u,size[u]);
}
int main()
{
//freopen("c.in","r",stdin);
int x;
scanf("%d%d",&n,&m);
scanf("%d%d",&c[1],&d[1]);
for (int i=2;i<=n;i++)
{
scanf("%d%d%d",&c[i],&d[i],&x);
son[x].push_back(i);
}
dfs(1);
//printf("%d\n",clo);
for (int i=n;;i--)
if (f[1][i]<=m)
{
printf("%d\n",i);
return 0;
}
}