LeetCode 94. Bianry Tree Inorder Traversal

LC address: https://leetcode.com/problems/binary-tree-inorder-traversal/

Given a binary tree, return the inorder traversal of its nodes’ values.

For example:
Given binary tree [1,null,2,3],

   1
    \
     2
    /
   3

return [1,3,2].

Analysis:

基本的stack的运用（或者用recursion）。

Solution:

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public List inorderTraversal(TreeNode root) {
        ArrayList list = new ArrayList();
 
        Stack stack = new Stack();
        TreeNode cur = root;
        
        while(!stack.empty() || cur != null){
            if (cur != null) {
                stack.push(cur);
                cur = cur.left;
            } else {
                cur = stack.pop();
                list.add(cur.val);
                cur = cur.right;
            }
        }
        
        return list;
    }
}

Solution code can also be found here: https://github.com/all4win/LeetCode.git