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63 lines
2.4 KiB
HTML
63 lines
2.4 KiB
HTML
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<p>给定一个正整数数组 <code>w</code> ，其中 <code>w[i]</code> 代表下标 <code>i</code> 的权重（下标从 <code>0</code> 开始），请写一个函数 <code>pickIndex</code> ，它可以随机地获取下标 <code>i</code>，选取下标 <code>i</code> 的概率与 <code>w[i]</code> 成正比。</p>
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<ol>
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</ol>
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<p>例如，对于 <code>w = [1, 3]</code>，挑选下标 <code>0</code> 的概率为 <code>1 / (1 + 3) = 0.25</code> （即，25%），而选取下标 <code>1</code> 的概率为 <code>3 / (1 + 3) = 0.75</code>（即，75%）。</p>
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<p>也就是说，选取下标 <code>i</code> 的概率为 <code>w[i] / sum(w)</code> 。</p>
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<p> </p>
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<p><strong>示例 1：</strong></p>
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<pre>
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<strong>输入：</strong>
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inputs = ["Solution","pickIndex"]
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inputs = [[[1]],[]]
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<strong>输出：</strong>
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[null,0]
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<strong>解释：</strong>
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Solution solution = new Solution([1]);
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solution.pickIndex(); // 返回 0，因为数组中只有一个元素，所以唯一的选择是返回下标 0。</pre>
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<p><strong>示例 2：</strong></p>
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<pre>
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<strong>输入：</strong>
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inputs = ["Solution","pickIndex","pickIndex","pickIndex","pickIndex","pickIndex"]
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inputs = [[[1,3]],[],[],[],[],[]]
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<strong>输出：</strong>
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[null,1,1,1,1,0]
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<strong>解释：</strong>
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Solution solution = new Solution([1, 3]);
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solution.pickIndex(); // 返回 1，返回下标 1，返回该下标概率为 3/4 。
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solution.pickIndex(); // 返回 1
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solution.pickIndex(); // 返回 1
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solution.pickIndex(); // 返回 1
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solution.pickIndex(); // 返回 0，返回下标 0，返回该下标概率为 1/4 。
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由于这是一个随机问题，允许多个答案，因此下列输出都可以被认为是正确的:
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[null,1,1,1,1,0]
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[null,1,1,1,1,1]
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[null,1,1,1,0,0]
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[null,1,1,1,0,1]
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[null,1,0,1,0,0]
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......
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诸若此类。
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</pre>
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<p> </p>
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<p><strong>提示：</strong></p>
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<ul>
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<li><code>1 <= w.length <= 10000</code></li>
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<li><code>1 <= w[i] <= 10^5</code></li>
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<li><code>pickIndex</code> 将被调用不超过 <code>10000</code> 次</li>
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</ul>
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<p> </p>
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<p><meta charset="UTF-8" />注意：本题与主站 528 题相同： <a href="https://leetcode-cn.com/problems/random-pick-with-weight/">https://leetcode-cn.com/problems/random-pick-with-weight/</a></p>
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