0pts但Unaccepted求调

#include<bits/stdc++.h>
using namespace std;
int cl[100005];
vector<int> tree[int(1e5)+5];
int ans=0;
bool dfs(int x){
    bool flag=0;
    for(auto it:tree[x]){
        if(dfs(it)){
            flag=1;
        }
    }
    if(flag&&cl[x]==0){
        ans++;
    }
    return (flag||(cl[x]==1));
}
int main(){
    int n;
    scanf("%d",&n);
    for(int i=1;i<=n;i++){
        scanf("%d",&cl[i]); //0白1黑
    }
    for(int i=1;i<n;i++){
        int a,b;
        scanf("%d",&a,&b);
        tree[a].push_back(b);
    }
    int rt=-1;
    for(int i=1;i<=n;i++){
        if(cl[i]==1){
            rt=i;
            break;
        }
    }
    dfs(rt);
    cout<<ans;

    return 0;
}