12-2 Kefa and Park

#include<iostream>
#include<vector>
#include<set>
#include<map>
#include<unordered_map>
using namespace std;
unordered_map<char,int>temp;
int cat[100005];
unordered_map<int,vector<int>>child;
void dfs(int pre,int now,int&res,const int&n,int cats)
{
    if(cats>n)
        return;
    if(!child[now].size())
    {
        //cout<<now<<"*****"<<endl;
        ++res;
        return;
    }
    for(int i=0;i!=child[now].size();++i)
    {
        dfs(now,child[now][i],res,n,cat[child[now][i]]?cats+cat[child[now][i]]:0);
    }
}
int main()
{
    int n,m;
    cin>>n>>m;
    for(int i=1;i<=n;++i)
        cin>>cat[i];
    int p,q;
    for(int i=0;i<n-1;++i)
    {
        cin>>p>>q;
        child[p].push_back(q);
    }
    int res=0;
    dfs(-1,1,res,m,cat[1]);
    cout<<res<<endl;
}