zoukankan      html  css  js  c++  java
  • [LC] 545. Boundary of Binary Tree

    Given a binary tree, return the values of its boundary in anti-clockwise direction starting from root. Boundary includes left boundary, leaves, and right boundary in order without duplicate nodes.  (The values of the nodes may still be duplicates.)

    Left boundary is defined as the path from root to the left-most node. Right boundary is defined as the path from root to the right-most node. If the root doesn't have left subtree or right subtree, then the root itself is left boundary or right boundary. Note this definition only applies to the input binary tree, and not applies to any subtrees.

    The left-most node is defined as a leaf node you could reach when you always firstly travel to the left subtree if exists. If not, travel to the right subtree. Repeat until you reach a leaf node.

    The right-most node is also defined by the same way with left and right exchanged.

    Example 1

    Input:
      1
       
        2
       / 
      3   4
    
    Ouput:
    [1, 3, 4, 2]
    
    Explanation:
    The root doesn't have left subtree, so the root itself is left boundary.
    The leaves are node 3 and 4.
    The right boundary are node 1,2,4. Note the anti-clockwise direction means you should output reversed right boundary.
    So order them in anti-clockwise without duplicates and we have [1,3,4,2].
    

    Example 2

    Input:
        ____1_____
       /          
      2            3
     /           / 
    4   5        6   
       /       / 
      7   8    9  10  
           
    Ouput:
    [1,2,4,7,8,9,10,6,3]
    
    Explanation:
    The left boundary are node 1,2,4. (4 is the left-most node according to definition)
    The leaves are node 4,7,8,9,10.
    The right boundary are node 1,3,6,10. (10 is the right-most node).
    So order them in anti-clockwise without duplicate nodes we have [1,2,4,7,8,9,10,6,3].

    Time: O(N)
    /**
     * Definition for a binary tree node.
     * public class TreeNode {
     *     int val;
     *     TreeNode left;
     *     TreeNode right;
     *     TreeNode(int x) { val = x; }
     * }
     */
    class Solution {
        List<Integer> res;
        public List<Integer> boundaryOfBinaryTree(TreeNode root) {
            res = new ArrayList<>();
            if (root == null) {
                return res;
            }
            res.add(root.val);
            leftTraversal(root.left);
            // exclude case [1]
            leafTraversal(root.left);
            leafTraversal(root.right);
            rightTraversal(root.right);
            return res;
        }
        
        private void leftTraversal(TreeNode root) {
            if (root == null || root.left == null && root.right == null) {
                return;
            }
            res.add(root.val);
            if (root.left != null) {
                leftTraversal(root.left);
            } else {
                leftTraversal(root.right);
            }
        }
        
        private void rightTraversal(TreeNode root) {
            if (root == null || root.left == null && root.right == null) {
                return;
            }
            if (root.right != null) {
                rightTraversal(root.right);
            } else {
                rightTraversal(root.left);
            }
            res.add(root.val);
        }
        
        private void leafTraversal(TreeNode root) {
            if (root == null) {
                return;
            }
            if (root.left == null && root.right == null) {
                res.add(root.val);
            }
            leafTraversal(root.left);
            leafTraversal(root.right);
        }
    }
  • 相关阅读:
    .NET写的Email可以群发邮件的实用函数
    動網中用到的幾個Function和一個JS[base64encode,base64decode,md5,sendmail,js]
    HTML在线编辑器
    IIS虚拟目录控制类
    实用正则表达式(实用篇)
    IIS站点管理类
    精巧sql语句
    圖片滾動代碼
    c# 添加图片水印,可以指定水印位置+生成缩略图
    JavaScript旋转图片
  • 原文地址:https://www.cnblogs.com/xuanlu/p/12708201.html
Copyright © 2011-2022 走看看