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36 lines
1.6 KiB
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36 lines
1.6 KiB
HTML
<p>Given an integer array <code>nums</code> with possible <strong>duplicates</strong>, randomly output the index of a given <code>target</code> number. You can assume that the given target number must exist in the array.</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(int[] nums)</code> Initializes the object with the array <code>nums</code>.</li>
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<li><code>int pick(int target)</code> Picks a random index <code>i</code> from <code>nums</code> where <code>nums[i] == target</code>. If there are multiple valid i's, then each index should have an equal probability of returning.</li>
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</ul>
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<p> </p>
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<p><strong>Example 1:</strong></p>
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<pre>
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<strong>Input</strong>
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["Solution", "pick", "pick", "pick"]
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[[[1, 2, 3, 3, 3]], [3], [1], [3]]
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<strong>Output</strong>
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[null, 4, 0, 2]
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<strong>Explanation</strong>
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Solution solution = new Solution([1, 2, 3, 3, 3]);
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solution.pick(3); // It should return either index 2, 3, or 4 randomly. Each index should have equal probability of returning.
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solution.pick(1); // It should return 0. Since in the array only nums[0] is equal to 1.
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solution.pick(3); // It should return either index 2, 3, or 4 randomly. Each index 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><code>1 <= nums.length <= 2 * 10<sup>4</sup></code></li>
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<li><code>-2<sup>31</sup> <= nums[i] <= 2<sup>31</sup> - 1</code></li>
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<li><code>target</code> is an integer from <code>nums</code>.</li>
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<li>At most <code>10<sup>4</sup></code> calls will be made to <code>pick</code>.</li>
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</ul>
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