1 ///L2-011. 玩转二叉树
 2 #include<iostream>
 3 #include<cstring>
 4 #include<queue>
 5 #include<cstdio>
 6 using namespace std;
 7 bool fist;
 8 const int maxn=40;
 9 struct tree_node
10 {
11   int value;
12   tree_node* leftchild;
13   tree_node* rightchild;
14   tree_node()
15   {
16     leftchild=NULL;
17     rightchild=NULL;
18   }
19 };
20 /**
21     根据中序遍历，前序遍历建树
22     递归 忽略细节  深入至所有结点建立
23 */
24 tree_node* build_tree(int pre[],int in[],int length)
25 {
26   if(length==0)return NULL;///终止条件
27   tree_node* temp = new tree_node;
28   int pos;
29   for(pos=0;pos<length;pos++)///找到根节点->然后根据中序遍历把左子树和右子树分开
30   {
31     if(in[pos]==pre[0])break;
32   }
33   temp->value=pre[0];
34   temp->leftchild=build_tree(pre+1,in,pos);
35   temp->rightchild=build_tree(pre+pos+1,in+pos+1,length-pos-1);
36   return temp;
37 }
38 /**
39     层次遍历镜面输出
40 */
41 void dfs(tree_node* tree)
42 {
43   queue<tree_node*>Q;
44   while(!Q.empty())Q.pop();///置空队列
45   Q.push(tree);
46   tree_node* root;
47   while(!Q.empty())
48   {
49     root=Q.front();
50     Q.pop();
51     if(!fist)///根节点输出
52     {
53       cout<<root->value;
54       fist=true;
55     }
56     else cout<<" "<<root->value;
57 
58     if(root->rightchild!=NULL)///先右后左即镜面输出
59     {
60       Q.push(root->rightchild);
61     }
62     if(root->leftchild!=NULL)
63     {
64       Q.push(root->leftchild);
65     }
66   }
67   cout<<endl;
68 }
69 int main()
70 {
71   int n;
72   int pre[maxn],in[maxn];
73   while(scanf("%d",&n)==1)
74   {
75     fist=false;
76     ///input
77     for(int i=0;i<n;i++)scanf("%d",&in[i]);
78     for(int i=0;i<n;i++)scanf("%d",&pre[i]);
79     ///solve
80     tree_node* tree=build_tree(pre,in,n);
81     dfs(tree);
82   }
83 }