Published on

[LeetCode 94] Binary Tree Inorder Traversal

Problem

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]

Constraints:

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

TypeScript

/**
 * Definition for a binary tree node.
 * class TreeNode {
 *     val: number
 *     left: TreeNode | null
 *     right: TreeNode | null
 *     constructor(val?: number, left?: TreeNode | null, right?: TreeNode | null) {
 *         this.val = (val===undefined ? 0 : val)
 *         this.left = (left===undefined ? null : left)
 *         this.right = (right===undefined ? null : right)
 *     }
 * }
 */

function inorderTraversal(root: TreeNode | null): number[] {
    const res: number[] = [];
    
    const run = (node: TreeNode): void => {
        if(node === null) return ;
        
        run(node.left)
        res.push(node.val)
        run(node.right)
    }
    
    run(root)
    return res;
};

Reference