94.InorderTraversal.cs

// 94. Binary Tree Inorder Traversal

// Given the root of a binary tree, return the inorder traversal of its nodes' values.
// Example 1:
// Input: root = [1,null,2,3]
// Output: [1,3,2]
// Example 2:
// Input: root = []
// Output: []
// Example 3:
// Input: root = [1]
// Output: [1]

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     public int val;
 *     public TreeNode left;
 *     public TreeNode right;
 *     public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
public class Solution {
    public IList<int> InorderTraversal(TreeNode root)
    {
        IList<int> result = new List<int>();
        if(root == null)
            return result;
        return Inorder(root,result);
    }
    public IList<int> Inorder(TreeNode root, IList<int> result)
    {
        if(root.left != null)
        {
            Inorder(root.left, result);
        }
        result.Add(root.val);
        if (root.right != null)
        {
            Inorder(root.right, result);
        }
        return result;
    }
}