1127 ZigZagging on a Tree（30 分）

#include
#include
#include
#include
using namespace std;
const int maxn = 50;
struct node {
    int data, layer;
    node *lchild, *rchild;
};
int n;
int in[maxn], post[maxn];
vectorans[maxn];
node* creat(int postL,int postR,int inL,int inR)
{
    if (postL > postR)return NULL;
    node* root = new node;
    root->data = post[postR];
    int k;
    for (k = inL; k <= inR; k++)
    {
        if (in[k] == root->data)break;
    }
    int leftnum = k - inL;
    root->lchild = creat(postL, postL + leftnum - 1, inL, k - 1);
    root->rchild = creat(postL + leftnum, postR-1, k + 1, inR);
    return root;
}
int maxlayer = 0;
void layerorder(node*root)
{
    root->layer = 0;
    queueq;
    q.push(root);
    while (!q.empty())
    {
        node* front = q.front();
        q.pop();
        ans[front->layer].push_back(front->data);
        maxlayer = max(maxlayer, front->layer);
        if (front->lchild)front->lchild->layer = front->layer + 1, q.push(front->lchild);
        if (front->rchild)front->rchild->layer = front->layer + 1, q.push(front->rchild);
    }
}
int main()
{
    scanf("%d", &n);
    for (int i = 0; i < n; i++)scanf("%d", &in[i]);
    for (int i = 0; i < n; i++)scanf("%d", &post[i]);
    node* root = creat(0, n - 1, 0, n - 1);
    layerorder(root);
    int cnt = 0;
    for (int i = 0; i <= maxlayer; i++)
    {
        if (i % 2 == 0)reverse(ans[i].begin(), ans[i].end());
        for (auto it = ans[i].begin(); it != ans[i].end(); it++)
        {
            printf("%d", *it);
            cnt++;
            if (cnt != n)printf(" ");
        }
    }
    return 0;
}