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41 lines
2.3 KiB
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<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>
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<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>
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<ul>
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<li><code>'L'</code> means to go from a node to its <strong>left child</strong> node.</li>
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<li><code>'R'</code> means to go from a node to its <strong>right child</strong> node.</li>
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<li><code>'U'</code> means to go from a node to its <strong>parent</strong> node.</li>
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</ul>
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<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>
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<p> </p>
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<p><strong class="example">Example 1:</strong></p>
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<img alt="" src="https://assets.leetcode.com/uploads/2021/11/15/eg1.png" style="width: 214px; height: 163px;" />
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<pre>
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<strong>Input:</strong> root = [5,1,2,3,null,6,4], startValue = 3, destValue = 6
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<strong>Output:</strong> "UURL"
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<strong>Explanation:</strong> The shortest path is: 3 → 1 → 5 → 2 → 6.
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</pre>
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<p><strong class="example">Example 2:</strong></p>
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<img alt="" src="https://assets.leetcode.com/uploads/2021/11/15/eg2.png" style="width: 74px; height: 102px;" />
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<pre>
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<strong>Input:</strong> root = [2,1], startValue = 2, destValue = 1
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<strong>Output:</strong> "L"
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<strong>Explanation:</strong> The shortest path is: 2 → 1.
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</pre>
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<p> </p>
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<p><strong>Constraints:</strong></p>
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<ul>
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<li>The number of nodes in the tree is <code>n</code>.</li>
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<li><code>2 <= n <= 10<sup>5</sup></code></li>
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<li><code>1 <= Node.val <= n</code></li>
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<li>All the values in the tree are <strong>unique</strong>.</li>
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<li><code>1 <= startValue, destValue <= n</code></li>
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<li><code>startValue != destValue</code></li>
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</ul>
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