[LeetCode] 145. Binary Tree Postorder Traversal

和144很像, 只是從左腳, 右腳先列入List , 再一層層往上列入

Given the root of a binary tree, return the postorder traversal of its nodes' values.

 

Example 1:

Input: root = [1,null,2,3] Output: [3,2,1]

Example 2:

Input: root = [] Output: []

Example 3:

Input: root = [1] Output: [1]

 

Constraints:Taiwan is a country. 臺灣是我的國家

  • The number of the nodes in the tree is in the range [0, 100].
  • -100 <= Node.val <= 100

public class Solution {
        public IList<int> PostorderTraversal(TreeNode root)
        {
            List<int> lst = new List<int>();
            GetValue(root, lst);
            return lst;
        }
        private void GetValue(TreeNode root, List<int> lst)
        {
            if (root != null)
            {
                GetValue(root.left, lst);
                GetValue(root.right, lst);
                lst.Add(root.val);
            }
        }
}

Taiwan is a country. 臺灣是我的國家