代码如下，有注释

#include <bits/stdc++.h>
#define N 100005
#define ll long long
#define ull unsigned long long
#define il inline
#define rg register
using namespace std;
struct node
{
    int lc, rc;
    int deep;
} a[1000001];
int main()
{
    cin.sync_with_stdio(false);
    int n;
    cin >> n;
    a[1].deep = 1; //根节点深度为1
    for (int i = 1; i <= n; i++)
    {
        cin >> a[i].lc >> a[i].rc;
        a[a[i].lc].deep = a[i].deep + 1;
        a[a[i].rc].deep = a[i].deep + 1;
        //孩子节点深度为父节点深度+1
    }
    int ans = 0;
    for (int i = 1; i <= n; i++)
        ans = max(ans, a[i].deep);//找最大深度节点的深度
    cout << ans << endl;
    system("pause");
    return 0;
}