zoukankan      html  css  js  c++  java
  • 1043 Is It a Binary Search Tree

    A Binary Search Tree (BST) is recursively defined as a binary tree which has the following properties:

    • The left subtree of a node contains only nodes with keys less than the node's key.
    • The right subtree of a node contains only nodes with keys greater than or equal to the node's key.
    • Both the left and right subtrees must also be binary search trees.

    If we swap the left and right subtrees of every node, then the resulting tree is called the Mirror Image of a BST.

    Now given a sequence of integer keys, you are supposed to tell if it is the preorder traversal sequence of a BST or the mirror image of a BST.

    Input Specification:

    Each input file contains one test case. For each case, the first line contains a positive integer N (≤). Then N integer keys are given in the next line. All the numbers in a line are separated by a space.

    Output Specification:

    For each test case, first print in a line YES if the sequence is the preorder traversal sequence of a BST or the mirror image of a BST, or NO if not. Then if the answer is YES, print in the next line the postorder traversal sequence of that tree. All the numbers in a line must be separated by a space, and there must be no extra space at the end of the line.

    Sample Input 1:

    7
    8 6 5 7 10 8 11
    
     

    Sample Output 1:

    YES
    5 7 6 8 11 10 8
    
     

    Sample Input 2:

    7
    8 10 11 8 6 7 5
    
     

    Sample Output 2:

    YES
    11 8 10 7 5 6 8
    
     

    Sample Input 3:

    7
    8 6 8 5 10 9 11
    
     

    Sample Output 3:

    NO

    题意:

      给出一个数字序列,问这个序列是不是一棵BST或者Mirror BST前序遍历的结果,如果是则输出对应树的后序遍历结果,如果不是则输出NO。

    思路:

      施工中………………

    Code:

     1 #include <bits/stdc++.h>
     2 
     3 using namespace std;
     4 
     5 int n;
     6 vector<int> v;
     7 vector<int> post;
     8 
     9 typedef struct Node* node;
    10 
    11 struct Node {
    12     int val;
    13     node left;
    14     node right;
    15     Node(int v) {
    16         val = v;
    17         left = NULL;
    18         right = NULL;
    19     }
    20 };
    21 
    22 bool isBST() {
    23     bool found1 = false;
    24     for (int i = 1; i < n; ++i) {
    25         if (v[i] >= v[0]) found1 = true;
    26         if (found1 && v[i] < v[0]) return false;
    27     }
    28     return true;
    29 }
    30 
    31 bool isMIBST() {
    32     bool found2 = false;
    33     for (int i = 1; i < n; ++i) {
    34         if (v[i] < v[0]) found2 = true;
    35         if (found2 && v[i] >= v[0]) return false;
    36     }
    37     return true;
    38 }
    39 
    40 node buildTree(int s, int e, bool isBST) {
    41     if (s > e) return NULL;
    42     node root = new Node(v[s]);
    43     int pos = -1;
    44     if (isBST) {
    45         for (int i = s + 1; i <= e; ++i)
    46             if (v[i] >= v[s]) {
    47                 pos = i;
    48                 break;
    49             }
    50     } else {
    51         for (int i = s + 1; i <= e; ++i)
    52             if (v[i] < v[s]) {
    53                 pos = i;
    54                 break;
    55             }
    56     }
    57     if (pos == -1) return root;
    58     root->left = buildTree(s + 1, pos - 1, isBST);
    59     root->right = buildTree(pos, e, isBST);
    60     return root;
    61 }
    62 
    63 void postOrder(node root) {
    64     if (root == NULL) return;
    65     postOrder(root->left);
    66     postOrder(root->right);
    67     post.push_back(root->val);
    68 }
    69 
    70 int main() {
    71     cin >> n;
    72     v.resize(n + 1);
    73     for (int i = 0; i < n; ++i) cin >> v[i];
    74     node root;
    75     if (isBST()) {
    76         cout << "YES" << endl;
    77         root = buildTree(0, n - 1, true);
    78     } else if (isMIBST()) {
    79         cout << "YES" << endl;
    80         root = buildTree(0, n - 1, false);
    81     } else {
    82         cout << "NO" << endl;
    83         return 0;
    84     }
    85     postOrder(root);
    86     bool isFirst = true;
    87     for (int i : post) {
    88         if (isFirst) {
    89             cout << i;
    90             isFirst = false;
    91         } else {
    92             cout << " " << i;
    93         }
    94     }
    95     cout << endl;
    96     return 0;
    97 }

    注意:

      上面的代码有三组数据不能通过,有时间再更正…………

  • 相关阅读:
    mongo 查询某个字段的值不为空列表!
    pdftohtml的使用
    Activiti数据库表结构(表详细版)
    ElasticSearch在linux上安装部署
    构建Spring Web应用程序—关于spring中的validate注解后台校验的解析
    构建Spring Web应用程序—SpringMVC详解
    高级装配—运行时注入
    高级装配—bean的作用域
    高级装配—条件化的Bean
    高级装配—配置profile bean
  • 原文地址:https://www.cnblogs.com/h-hkai/p/12865952.html
Copyright © 2011-2022 走看看