字节跳动第四题为什么没有ac啊

#include <iostream> #include <vector> using namespace std;  void dp(int l,int n,long long sum,vector<vector<int>> &rec, vector<long long> &res)
{ long long record=sum;  for(int i=l;i<=n;i++)
    { for(int j=i+1;j<=n;j++)
        {
            sum=record;  if(rec[i][j]==1)
            {
                sum+=1;  int a=sum%3;  if(a==0)
                {
                    res[0]+=sum;  }else if(a==1)
                {
                    res[1]+=sum;  }else{
                    res[2]+=sum;   }
                dp(j,n,sum,rec,res);  }
        }
    }
}  int main() { int n=0;  cin>>n;  long long sum=0;  vector<int> temp(n+1,0);  vector<long long> res(3,0);  vector<vector<int>> rec(n+1,temp);   int a=0,b=0;  for(int i=0;i<n-1;i++)
    {
        cin>>a>>b;  rec[a][b]=1;  rec[b][a]=1;   } for(int i=1;i<=n;i++)
    { for(int j=i+1;j<=n;j++)
        {
            sum=0;  if(rec[i][j]==1)
            {
                sum+=1;  int a=sum%3;  if(a==0)
                {
                    res[0]+=sum;  }else if(a==1)
                {
                    res[1]+=sum;  }else{
                    res[2]+=sum;   }
                dp(j,n,sum,rec,res);  }
        }
    } long cout1=res[0]%(1000000007);  long cout2=res[1]%(1000000007);  long cout3=res[2]%(1000000007);  cout<<cout1<<' '<<cout2<<' '<<cout3;   return 0; }