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55 lines
3.0 KiB
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<p>An element <code>x</code> of an integer array <code>arr</code> of length <code>m</code> is <strong>dominant</strong> if <code>freq(x) * 2 > m</code>, where <code>freq(x)</code> is the number of occurrences of <code>x</code> in <code>arr</code>. Note that this definition implies that <code>arr</code> can have <strong>at most one</strong> dominant element.</p>
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<p>You are given a <strong>0-indexed</strong> integer array <code>nums</code> of length <code>n</code> with one dominant element.</p>
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<p>You can split <code>nums</code> at an index <code>i</code> into two arrays <code>nums[0, ..., i]</code> and <code>nums[i + 1, ..., n - 1]</code>, but the split is only <strong>valid</strong> if:</p>
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<ul>
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<li><code>0 <= i < n - 1</code></li>
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<li><code>nums[0, ..., i]</code>, and <code>nums[i + 1, ..., n - 1]</code> have the same dominant element.</li>
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</ul>
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<p>Here, <code>nums[i, ..., j]</code> denotes the subarray of <code>nums</code> starting at index <code>i</code> and ending at index <code>j</code>, both ends being inclusive. Particularly, if <code>j < i</code> then <code>nums[i, ..., j]</code> denotes an empty subarray.</p>
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<p>Return <em>the <strong>minimum</strong> index of a <strong>valid split</strong></em>. If no valid split exists, return <code>-1</code>.</p>
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<p> </p>
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<p><strong class="example">Example 1:</strong></p>
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<pre>
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<strong>Input:</strong> nums = [1,2,2,2]
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<strong>Output:</strong> 2
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<strong>Explanation:</strong> We can split the array at index 2 to obtain arrays [1,2,2] and [2].
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In array [1,2,2], element 2 is dominant since it occurs twice in the array and 2 * 2 > 3.
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In array [2], element 2 is dominant since it occurs once in the array and 1 * 2 > 1.
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Both [1,2,2] and [2] have the same dominant element as nums, so this is a valid split.
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It can be shown that index 2 is the minimum index of a valid split. </pre>
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<p><strong class="example">Example 2:</strong></p>
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<pre>
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<strong>Input:</strong> nums = [2,1,3,1,1,1,7,1,2,1]
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<strong>Output:</strong> 4
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<strong>Explanation:</strong> We can split the array at index 4 to obtain arrays [2,1,3,1,1] and [1,7,1,2,1].
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In array [2,1,3,1,1], element 1 is dominant since it occurs thrice in the array and 3 * 2 > 5.
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In array [1,7,1,2,1], element 1 is dominant since it occurs thrice in the array and 3 * 2 > 5.
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Both [2,1,3,1,1] and [1,7,1,2,1] have the same dominant element as nums, so this is a valid split.
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It can be shown that index 4 is the minimum index of a valid split.</pre>
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<p><strong class="example">Example 3:</strong></p>
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<pre>
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<strong>Input:</strong> nums = [3,3,3,3,7,2,2]
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<strong>Output:</strong> -1
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<strong>Explanation:</strong> It can be shown that there is no valid split.
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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 <= 10<sup>5</sup></code></li>
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<li><code>1 <= nums[i] <= 10<sup>9</sup></code></li>
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<li><code>nums</code> has exactly one dominant element.</li>
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</ul>
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