记录一个会超时的做法, acwing只能过一个数据...
pat网站超时一个数据
#include <iostream>
#include <algorithm>
#include <unordered_map>

using namespace std;

int n, root, max_depth;
int cnt[1010];
unordered_map<int, int> l, r;

void dfs(int father, int u, int depth)
{
    if(u <= father)
    {
        if(l.count(father) == 0)  //左孩子为空
        {
            l[father] = u;
            cnt[depth + 1] ++;
            max_depth = max(max_depth, depth + 1);
        }
        else dfs(l[father], u, depth + 1);
    }
    else if(u > father)
    {
        if(r.count(father) == 0)
        {
            r[father] = u;
            cnt[depth + 1] ++;
            max_depth = max(max_depth, depth + 1);
        }
        else dfs(r[father], u, depth + 1);
    }
}

int main()
{
    cin >> n;
    if(n == 1)
    {
        int x;
        cin >> x;
        cout << "1 + 0 = 1" << endl;
        return 0;
    }
    for(int i = 0; i < n; i ++)
    {
        int x;
        cin >> x;
        if(i == 0) root = x;
        else 
        {
            dfs(root, x, 0); //从第0层开始插入
        }
    }

    int a = cnt[max_depth], b = cnt[max_depth - 1];
    cout << a << " + " << b << " = " << a+b << endl;

    return 0;
}