#2096

Step-By-Step Directions From a Binary Tree Node to Another

medium · verified · 56.4% accepted · 3,250 likes · top 51%

string · tree · depth-first search · binary tree

Description

You are given the root of a binary tree with n nodes. Each node is uniquely assigned a value from 1 to n. You are also given an integer startValue representing the value of the start node s, and a different integer destValue representing the value of the destination node t.

Find the shortest path starting from node s and ending at node t. Generate step-by-step directions of such path as a string consisting of only the uppercase letters 'L', 'R', and 'U'. Each letter indicates a specific direction:

- 'L' means to go from a node to its left child node.

- 'R' means to go from a node to its right child node.

- 'U' means to go from a node to its parent node.

Return the step-by-step directions of the shortest path from node s to node t.

Example 1:

Input: root = [5,1,2,3,null,6,4], startValue = 3, destValue = 6

Output: "UURL"

Explanation: The shortest path is: 3 → 1 → 5 → 2 → 6.

Example 2:

Input: root = [2,1], startValue = 2, destValue = 1

Output: "L"

Explanation: The shortest path is: 2 → 1.

Solution