mirror of
https://gitee.com/coder-xiaomo/leetcode-problemset
synced 2025-01-11 02:58:13 +08:00
41 lines
2.3 KiB
HTML
41 lines
2.3 KiB
HTML
<p>You are given the <code>root</code> of a <strong>binary tree</strong> with <code>n</code> nodes. Each node is uniquely assigned a value from <code>1</code> to <code>n</code>. You are also given an integer <code>startValue</code> representing the value of the start node <code>s</code>, and a different integer <code>destValue</code> representing the value of the destination node <code>t</code>.</p>
|
|
|
|
<p>Find the <strong>shortest path</strong> starting from node <code>s</code> and ending at node <code>t</code>. Generate step-by-step directions of such path as a string consisting of only the <strong>uppercase</strong> letters <code>'L'</code>, <code>'R'</code>, and <code>'U'</code>. Each letter indicates a specific direction:</p>
|
|
|
|
<ul>
|
|
<li><code>'L'</code> means to go from a node to its <strong>left child</strong> node.</li>
|
|
<li><code>'R'</code> means to go from a node to its <strong>right child</strong> node.</li>
|
|
<li><code>'U'</code> means to go from a node to its <strong>parent</strong> node.</li>
|
|
</ul>
|
|
|
|
<p>Return <em>the step-by-step directions of the <strong>shortest path</strong> from node </em><code>s</code><em> to node</em> <code>t</code>.</p>
|
|
|
|
<p> </p>
|
|
<p><strong>Example 1:</strong></p>
|
|
<img alt="" src="https://assets.leetcode.com/uploads/2021/11/15/eg1.png" style="width: 214px; height: 163px;" />
|
|
<pre>
|
|
<strong>Input:</strong> root = [5,1,2,3,null,6,4], startValue = 3, destValue = 6
|
|
<strong>Output:</strong> "UURL"
|
|
<strong>Explanation:</strong> The shortest path is: 3 → 1 → 5 → 2 → 6.
|
|
</pre>
|
|
|
|
<p><strong>Example 2:</strong></p>
|
|
<img alt="" src="https://assets.leetcode.com/uploads/2021/11/15/eg2.png" style="width: 74px; height: 102px;" />
|
|
<pre>
|
|
<strong>Input:</strong> root = [2,1], startValue = 2, destValue = 1
|
|
<strong>Output:</strong> "L"
|
|
<strong>Explanation:</strong> The shortest path is: 2 → 1.
|
|
</pre>
|
|
|
|
<p> </p>
|
|
<p><strong>Constraints:</strong></p>
|
|
|
|
<ul>
|
|
<li>The number of nodes in the tree is <code>n</code>.</li>
|
|
<li><code>2 <= n <= 10<sup>5</sup></code></li>
|
|
<li><code>1 <= Node.val <= n</code></li>
|
|
<li>All the values in the tree are <strong>unique</strong>.</li>
|
|
<li><code>1 <= startValue, destValue <= n</code></li>
|
|
<li><code>startValue != destValue</code></li>
|
|
</ul>
|