Sync LeetCode submission Runtime - 115 ms (24.26%), Memory - 34.6 MB (24.26%)

Author: jimit105

2888-minimum-index-of-a-valid-split/README.md

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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 <strong>more than half</strong> the elements of <code>arr</code> have a value of <code>x</code>.</p>
+
+<p>You are given a <strong>0-indexed</strong> integer array <code>nums</code> of length <code>n</code> with one <strong>dominant</strong> element.</p>
+
+<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>
+
+<ul>
+	<li><code>0 &lt;= i &lt; n - 1</code></li>
+	<li><code>nums[0, ..., i]</code>, and <code>nums[i + 1, ..., n - 1]</code> have the same dominant element.</li>
+</ul>
+
+<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 &lt; i</code> then <code>nums[i, ..., j]</code> denotes an empty subarray.</p>
+
+<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>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+
+<pre>
+<strong>Input:</strong> nums = [1,2,2,2]
+<strong>Output:</strong> 2
+<strong>Explanation:</strong> We can split the array at index 2 to obtain arrays [1,2,2] and [2]. 
+In array [1,2,2], element 2 is dominant since it occurs twice in the array and 2 * 2 &gt; 3. 
+In array [2], element 2 is dominant since it occurs once in the array and 1 * 2 &gt; 1.
+Both [1,2,2] and [2] have the same dominant element as nums, so this is a valid split. 
+It can be shown that index 2 is the minimum index of a valid split. </pre>
+
+<p><strong class="example">Example 2:</strong></p>
+
+<pre>
+<strong>Input:</strong> nums = [2,1,3,1,1,1,7,1,2,1]
+<strong>Output:</strong> 4
+<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].
+In array [2,1,3,1,1], element 1 is dominant since it occurs thrice in the array and 3 * 2 &gt; 5.
+In array [1,7,1,2,1], element 1 is dominant since it occurs thrice in the array and 3 * 2 &gt; 5.
+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.
+It can be shown that index 4 is the minimum index of a valid split.</pre>
+
+<p><strong class="example">Example 3:</strong></p>
+
+<pre>
+<strong>Input:</strong> nums = [3,3,3,3,7,2,2]
+<strong>Output:</strong> -1
+<strong>Explanation:</strong> It can be shown that there is no valid split.
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>1 &lt;= nums.length &lt;= 10<sup>5</sup></code></li>
+	<li><code>1 &lt;= nums[i] &lt;= 10<sup>9</sup></code></li>
+	<li><code>nums</code> has exactly one dominant element.</li>
+</ul>

2888-minimum-index-of-a-valid-split/solution.py

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+# Approach 1: Hash Map
+
+# Time: O(n)
+# Space: O(n)
+
+from collections import defaultdict
+
+class Solution:
+    def minimumIndex(self, nums: List[int]) -> int:
+        first_map = defaultdict(int)
+        second_map = defaultdict(int)
+        n = len(nums)
+
+        for num in nums:
+            second_map[num] += 1
+
+        for index in range(n):
+            num = nums[index]
+            second_map[num] -= 1
+            first_map[num] += 1
+
+            if first_map[num] * 2 > index + 1 and second_map[num] * 2 > n - index - 1:
+                return index
+
+        return -1
+