lintcode 访问路径
http://www.lintcode.com/zh-cn/problem/binary-tree-inorder-traversal/
描述
给出一棵二叉树,返回其中序遍历。
样例
给出二叉树{1, #, 2, 3}
返回[1,3,2]。
何为二叉树中序遍历
顺序：左 -> 根 -> 右
获取到一个节点后，将其暂存，遍历完左子树后，再输出该节点的值，然后再遍历右子树。
Java代码实现
非递归实现
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| /**
* Definition of TreeNode:
* public class TreeNode {
* public int val;
* public TreeNode left, right;
* public TreeNode(int val) {
* this.val = val;
* this.left = this.right = null;
* }
* }
*/
public class Solution {
/**
* @param root: The root of binary tree.
* @return: Inorder in ArrayList which contains node values.
*/
public ArrayList<Integer> inorderTraversal(TreeNode root) {
// write your code here
Stack<TreeNode> treeNodeStack = new Stack<TreeNode>();
ArrayList<Integer> result = new ArrayList<Integer>();
TreeNode node = root;
while (node != null || !treeNodeStack.empty()) {
while (node != null) {
treeNodeStack.push(node);
node = node.left;
}
if (!treeNodeStack.empty()) {
node = treeNodeStack.pop();
result.add(node.val);
node = node.right;
}
}
return result;
}
}
|
递归实现
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| /**
* Definition of TreeNode:
* public class TreeNode {
* public int val;
* public TreeNode left, right;
* public TreeNode(int val) {
* this.val = val;
* this.left = this.right = null;
* }
* }
*/
public class Solution {
/**
* @param root: The root of binary tree.
* @return: Inorder in ArrayList which contains node values.
*/
public ArrayList<Integer> inorderTraversal(TreeNode root) {
// write your code here
ArrayList<Integer> result = new ArrayList<Integer>();
recursionMiddleorderTraversal(root, result);
return result;
}
public static void recursionMiddleorderTraversal(TreeNode root, ArrayList<Integer> result) {
if (root != null) {
recursionMiddleorderTraversal(root.left, result);
result.add(root.val);
recursionMiddleorderTraversal(root.right, result);
}
}
}
|
Python代码实现
非递归实现
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| """
Definition of TreeNode:
class TreeNode:
def __init__(self, val):
self.val = val
self.left, self.right = None, None
"""
class Solution:
"""
@param root: The root of binary tree.
@return: Inorder in ArrayList which contains node values.
"""
def inorderTraversal(self, root):
# write your code here
stack = []
result = []
node = root
while node or stack:
while node:
stack.append(node)
node = node.left
if stack:
node = stack.pop()
result.append(node.val)
node = node.right
return result
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递归实现
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| """
Definition of TreeNode:
class TreeNode:
def __init__(self, val):
self.val = val
self.left, self.right = None, None
"""
class Solution:
"""
@param root: The root of binary tree.
@return: Inorder in ArrayList which contains node values.
"""
def inorderTraversal(self, root):
# write your code here
if root is None:
return []
return self.inorderTraversal(root.left) + [root.val] + self.inorderTraversal(root.right)
|