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Author: jimit105

2766-find-the-prefix-common-array-of-two-arrays/README.md

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+<p>You are given two <strong>0-indexed </strong>integer<strong> </strong>permutations <code>A</code> and <code>B</code> of length <code>n</code>.</p>
+
+<p>A <strong>prefix common array</strong> of <code>A</code> and <code>B</code> is an array <code>C</code> such that <code>C[i]</code> is equal to the count of numbers that are present at or before the index <code>i</code> in both <code>A</code> and <code>B</code>.</p>
+
+<p>Return <em>the <strong>prefix common array</strong> of </em><code>A</code><em> and </em><code>B</code>.</p>
+
+<p>A sequence of <code>n</code> integers is called a&nbsp;<strong>permutation</strong> if it contains all integers from <code>1</code> to <code>n</code> exactly once.</p>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+
+<pre>
+<strong>Input:</strong> A = [1,3,2,4], B = [3,1,2,4]
+<strong>Output:</strong> [0,2,3,4]
+<strong>Explanation:</strong> At i = 0: no number is common, so C[0] = 0.
+At i = 1: 1 and 3 are common in A and B, so C[1] = 2.
+At i = 2: 1, 2, and 3 are common in A and B, so C[2] = 3.
+At i = 3: 1, 2, 3, and 4 are common in A and B, so C[3] = 4.
+</pre>
+
+<p><strong class="example">Example 2:</strong></p>
+
+<pre>
+<strong>Input:</strong> A = [2,3,1], B = [3,1,2]
+<strong>Output:</strong> [0,1,3]
+<strong>Explanation:</strong> At i = 0: no number is common, so C[0] = 0.
+At i = 1: only 3 is common in A and B, so C[1] = 1.
+At i = 2: 1, 2, and 3 are common in A and B, so C[2] = 3.
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>1 &lt;= A.length == B.length == n &lt;= 50</code></li>
+	<li><code>1 &lt;= A[i], B[i] &lt;= n</code></li>
+	<li><code>It is guaranteed that A and B are both a permutation of n integers.</code></li>
+</ul>

2766-find-the-prefix-common-array-of-two-arrays/solution.py

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+# Approach 3: Single Pass with Frequency Array
+
+# Time: O(n)
+# Space: O(n)
+
+class Solution:
+    def findThePrefixCommonArray(self, A: List[int], B: List[int]) -> List[int]:
+        n = len(A)
+        prefix_common_array = [0 for _ in range(n)]
+        freq = [0 for _ in range(n + 1)]
+        common_count = 0
+
+        for current_idx in range(n):
+            freq[A[current_idx]] += 1
+            if freq[A[current_idx]] == 2:
+                common_count += 1
+
+            freq[B[current_idx]] += 1
+            if freq[B[current_idx]] == 2:
+                common_count += 1
+
+            prefix_common_array[current_idx] = common_count
+
+        return prefix_common_array