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46 lines
1.8 KiB
HTML
46 lines
1.8 KiB
HTML
<p>Given a singly linked list, return a random node's value from the linked list. Each node must have the <strong>same probability</strong> of being chosen.</p>
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<p>Implement the <code>Solution</code> class:</p>
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<ul>
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<li><code>Solution(ListNode head)</code> Initializes the object with the head of the singly-linked list <code>head</code>.</li>
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<li><code>int getRandom()</code> Chooses a node randomly from the list and returns its value. All the nodes of the list should be equally likely to be chosen.</li>
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</ul>
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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/2021/03/16/getrand-linked-list.jpg" style="width: 302px; height: 62px;" />
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<pre>
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<strong>Input</strong>
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["Solution", "getRandom", "getRandom", "getRandom", "getRandom", "getRandom"]
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[[[1, 2, 3]], [], [], [], [], []]
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<strong>Output</strong>
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[null, 1, 3, 2, 2, 3]
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<strong>Explanation</strong>
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Solution solution = new Solution([1, 2, 3]);
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solution.getRandom(); // return 1
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solution.getRandom(); // return 3
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solution.getRandom(); // return 2
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solution.getRandom(); // return 2
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solution.getRandom(); // return 3
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// getRandom() should return either 1, 2, or 3 randomly. Each element should have equal probability of returning.
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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 linked list will be in the range <code>[1, 10<sup>4</sup>]</code>.</li>
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<li><code>-10<sup>4</sup> <= Node.val <= 10<sup>4</sup></code></li>
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<li>At most <code>10<sup>4</sup></code> calls will be made to <code>getRandom</code>.</li>
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</ul>
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<p> </p>
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<p><strong>Follow up:</strong></p>
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<ul>
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<li>What if the linked list is extremely large and its length is unknown to you?</li>
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<li>Could you solve this efficiently without using extra space?</li>
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</ul>
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