Mountaineering team (DFS)

Title Description ：

Main idea ：

I didn't see this topic clearly at first , I think everyone can choose a way to climb up .
Later, it was found that there was a person on each road , Then I have no idea .
Because I don't know how to judge that road, facing the problem of passing two people at the same time .
Then I saw dalao Code for , Or reverse from 1 Start , Each time, one person goes up from the next node on each road , I think it's wonderful ！

#include<iostream>
#include<algorithm>
#include<cstring>
#include<vector>
using namespace std;
int num[1010];
vector<int> l[1010];
int f[1010];// Record how many people there are at each point 
// One person on each node takes a step up to the next node 
void dfs(int x,int last)
{
    
    for(int i=0;i<l[x].size();i++)
    {
    
        int nowx=l[x][i];
        if(nowx!=last)
        {
    
            if(f[nowx])
            {
    
                f[nowx]-=1;
                f[x]+=1;
            }
            dfs(nowx,x);
        }
    }
}
int main()
{
    
    int n;
    cin>>n;
    for(int i=1;i<n;i++)
    {
    
        int x,y;
        cin>>x>>y;
        l[x].push_back(y);
        l[y].push_back(x);
        num[x]+=1;
        num[y]+=1;
    }
    int sum=0;
    for(int i=2;i<=n;i++)
    {
    
        if(num[i]==1) f[i]=1,sum+=1;
    }
    int ans=0;
    while(f[1]!=sum)
    {
    
        dfs(1,0);
        ans+=1;
    }
    cout<<ans<<endl;
    return 0;
}