根据前序中序创建二叉树以及层次遍历输出镜像树

acm

# include<iostream>
# include<string>
# include<algorithm>
#include<numeric>
#include <vector>
#include <queue>
using namespace std;
int mid[32], fr[32];
struct node {
    int l, r;
}a[1002];
//建一个以一个mid[la,ra],fr[lb,rb]所确定的数
int build(int la, int ra, int lb, int rb)
{
    if (la > ra)
        return 0;
    //fr:前序，b序列
    //mid:中序，a序列
    int rt = fr[lb], p1, p2;
    p1 = la;
    //找到pl对应的前序的第一个节点，也就是树的根。
    while (mid[p1] != rt) p1++;
    p2 = p1 - la;
    a[rt].l = build(la, p1 - 1, lb + 1, lb + p2);
    a[rt].r = build(p1 + 1, ra, lb + p2 + 1, rb);
    return rt;
}
void bfs(int x)
{
    queue<int>q;
    queue<int>v;
    q.push(x);
    while (!q.empty())
    {
        int w = q.front();
        q.pop();
        //if (w == 0)
        //  break;
        v.push(w);
        if (a[w].r != 0)
            q.push(a[w].r);
        if (a[w].l != 0)
            q.push(a[w].l);
    }
    while (!v.empty())
    {
        cout << v.front();
        v.pop();
    }
    return;
}
int main1()
{
    int n;
    cin >> n;
    for (int i = 0; i < n; i++) cin >> mid[i];
    for (int i = 0; i < n; i++) cin >> fr[i];
    int root = build(0, n - 1, 0, n - 1);
    bfs(root);
    system("pause");
    return 0;
}
# include <stack>
void test() {
    stack<int> s;
    priority_queue<int> q;
    for (int i = 1; i < 10; i++)
        s.push(i);
    for(int i = 1; i < 10; ++i)
        cout << s.top() << endl;    
    q.push(1);
    cout << q.top() << endl;
    q.pop();
    cout << q.empty();
}
int main() {
    test();
    system("pause");
    return 0;
}