c++里结构体指针的使用

#include<bits/stdc++.h>
using namespace std;
const int N = 25;

// 定义二叉树节点结构体
struct node {
    int val;
    node* l, *r;  // 改为指针类型
};

node v[N];
int mid[25];
int pos[25];
int you[25];
int zuo[25];

// 根据中序和后序遍历构建二叉树
node* build(int l, int r, int x, int y) {
    if (x > y) return nullptr;  // 使用 nullptr 表示空指针
    int ta = pos[y];
    node* head = new node;  // 创建新节点
    head->val = ta;  // 赋值

    if (x == y) return head;

    int t = 0;
    for (int i = 1; i <= r - l + 1; i++) {
        if (mid[l + i - 1] == ta) {
            t = i + l - 1;
            break;
        }
    }

    head->l = build(l, t - 1, x, x + t - l - 1);
    head->r = build(t + 1, r, x + t - l, y - 1);
    return head;
}

int main() {
    int n;
    cin >> n;  // 读取节点数量
    for (int i = 1; i <= n; i++) {
        cin >> mid[i];
    }
    for (int i = 1; i <= n; i++) {
        cin >> pos[i];
    }
    node* rt = build(1, n, 1, n);

    node* q[30];
    int hh = 0, tt = -1;
    q[++tt] = rt;

    int zz = 0, yy = 0;
    while (hh <= tt) {
        int sz = tt - hh + 1;
        for (int i = 0; i < sz; i++) {
            node* cur = q[hh++];
            if (i == 0) zuo[zz++] = cur->val;
            if (i == sz - 1) you[yy++] = cur->val;
            if (cur->l != nullptr) {
                q[++tt] = cur->l;
            }
            if (cur->r != nullptr) {
                q[++tt] = cur->r;
            }
        }
    }
cout<<"R:";  for (int i = 0; i < yy; i++) {

          cout << " " << you[i];
    }    cout << endl;
    cout<<"L:";
    for (int i = 0; i < zz; i++) {

        cout << " " << zuo[i];
    }



    return 0;
}