1127

#include <iostream>
#include <vector>
#include <queue>
using namespace std;

int n;
const int maxn = 31;
struct node { int data; node *l, *r;};
vector<int> post(maxn), in(maxn), ans, lnum(maxn);

node* build(int postL, int postR, int inL, int inR){//根据后序和中序建树
    if(postL > postR) return NULL;
    node *root = new node;
    root->data = post[postR];
    int k;
    for (k = inL; k <= inR; k++)
        if(in[k] == post[postR]) break;
    int numLeft = k - inL;
    root->l = build(postL, postL + numLeft - 1, inL, k - 1);
    root->r = build(postL + numLeft, postR - 1, k + 1, inR);
    return root;
}
void dfs(node *root, int depth){//求每一层的个数
    if (root == NULL) return;
    lnum[depth]++;
    if(root->l != NULL) dfs(root->l, depth + 1);
    if(root->r != NULL) dfs(root->r, depth + 1);
}
void bfs(node *root){//层序遍历的结果存在ans中
    queue<node*> q;
    q.push(root);
    while (!q.empty()) {
        node *now = q.front();
        q.pop();
        ans.push_back(now->data);
        if(now->l) q.push(now->l);
        if(now->r) q.push(now->r);
    }
}

int main(){
    cin >> n;
    for(int i = 0; i < n; i++) cin >> in[i];
    for(int i = 0; i < n; i++) cin >> post[i];
    node *root = build(0, n - 1, 0, n - 1);
    dfs(root, 0);
    bfs(root);
    //z输出
    int cnt = 0;
    printf("%d", ans[cnt++]);
    for (int i = 1; i < maxn;) {
        if (i % 2) {
            for (int j = 0; j < lnum[i]; j++)
                printf(" %d", ans[cnt+j]);
            cnt = cnt + lnum[i];
            i++;
        }else{
            for (int j = lnum[i] - 1; j >= 0; j--)
                printf(" %d", ans[cnt+j]);
            cnt = cnt + lnum[i];
            i++;
        }
    }
    cout << endl;

    return 0;
}

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转载自blog.csdn.net/qq_31474267/article/details/79596049