HDU-1710-二叉树 

 1 #include <iostream>
 2 using namespace std;
 3 
 4 typedef long long ll;
 5 
 6 const int maxn = 1010;
 7 
 8 // 输入先序遍历和中序遍历， 求后序遍历；
 9 
10 int pre[maxn], in[maxn], post[maxn];
11 int k;
12 
13 struct node
14 {
15     int value;
16     node *l, *r;
17     node(int value = 0, node *l = nullptr, node *r = nullptr):
18         value(value), l(l), r(r){}
19 };
20 
21 void buildtree_dfs(int l, int r, int &t, node* &root)
22 {
23     int flag = -1;
24     for(int i = l; i <= r; i++)
25     {
26         if(in[i] == pre[t])
27         {
28             flag = i;
29             break;
30         }
31     }
32     if(flag == -1) return;
33     root = new node(in[flag]);
34     t++;
35     if(flag > l) buildtree_dfs(l, flag - 1, t, root->l);
36     if(flag < r) buildtree_dfs(flag + 1, r, t, root->r);
37 }
38 
39 void preorder(node *root)
40 {
41     if(root != nullptr)
42     {
43         post[k++] = root->value;
44         preorder(root->l);
45         preorder(root->r);
46     }
47 }
48 
49 void inorder(node *root)
50 {
51     if(root != nullptr)
52     {
53         inorder(root->l);
54         post[k++] = root->value;
55         inorder(root->r);
56     }
57 }
58 
59 void postorder(node *root)
60 {
61     if(root != nullptr)
62     {
63         postorder(root->l);
64         postorder(root->r);
65         post[k++] = root->value;
66     }
67 }
68 
69 int main()
70 {
71     int n;
72     while(cin >> n)
73     {
74         for(int i = 1; i <= n; i++) cin >> pre[i];
75         for(int i = 1; i <= n; i++) cin >> in[i];
76         node *root;
77         int t = 1;
78         buildtree_dfs(1, n, t, root);
79         k = 0;
80         postorder(root);
81         for(int i = 0; i < k; i++)
82         {
83             cout << post[i];
84             if(i != k - 1) cout << " ";
85         }
86         cout << endl;
87     }
88     return 0;
89 }

 

posted @ 2020-09-08 20:45  章楠雨  阅读(152)  评论(0)    收藏  举报