[LeetCode94]Binary Tree Inorder Traversal
2015-08-31 22:45
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Binary Tree Inorder Traversal
Total Accepted: 80048 TotalSubmissions: 219796My Submissions
Question
Solution
Given a binary tree, return the inorder traversal of its nodes' values.
For example:
Given binary tree
{1,#,2,3},
1 \ 2 / 3
return
[1,3,2].
Note: Recursive solution is trivial, could you do it iteratively?
confused what
"{1,#,2,3}"means? >
read more on how binary tree is serialized on OJ.
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使用递归的方法
Code:
package com.leetcode.problems; import java.util.ArrayList; import java.util.List; class TreeNode { int val; TreeNode left; TreeNode right; TreeNode(int x) { val = x; } } public class Solution94 { public void recursion(TreeNode root,List<Integer> re){ if(root!=null){ if(root.left!=null){ recursion(root.left, re); } re.add(root.val); if(root.right!=null){ recursion(root.right, re); } } } public List<Integer> inorderTraversal(TreeNode root) { List<Integer> list = new ArrayList<Integer>(); if(root != null){ recursion(root,list); } return list; } public static void main(String[] args) { TreeNode tn1 = new TreeNode(1); TreeNode tn2 = new TreeNode(2); TreeNode tn3 = new TreeNode(3); tn1.left = null; tn1.right = tn2; tn2.left = tn3; tn2.right = null; tn3.left = null; tn3.right = null; List<Integer> list = new Solution94().inorderTraversal(tn1); for(Integer i:list){ System.out.println(i); } } }
方式二:使用栈的方式
public List<Integer> inorderTraversal(TreeNode root) { List<Integer> list = new ArrayList<Integer>(); Stack<TreeNode> stack = new Stack<TreeNode>(); TreeNode cur = root; while(cur!=null || !stack.isEmpty()){ while(cur!=null){ stack.push(cur); cur = cur.left; } cur = stack.pop(); list.add(cur.val); cur = cur.right; } return list; }
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