[Hacker Rank] Interview Preparation Kit: Miscellaneous: Maximum Xor. First steps.

Author: Gonzalo Diaz

docs/hackerrank/interview_preparation_kit/miscellaneous/maximum-xor.md

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+# [Miscellaneous: Maximum Xor](https://www.hackerrank.com/challenges/maximum-xor)
+
+- Difficulty:  `#medium`
+- Category: `#Miscellaneous`
+
+Find the maximum xor value in the array.
+
+You are given an array `arr` of `n` elements.
+A list of integers, `queries` is given as an input,
+find the maximum value of
+`queries[j]` $ \oplus $ `each arr[i]`
+for all $ 0 \leq i < n $,
+where \oplus represents [xor](https://en.wikipedia.org/wiki/Exclusive_or)
+of two elements.
+
+Note that there are multiple test cases in one input file.
+
+For example:
+
+$ \begin{array}{ll}
+arr &= [3, 7, 15, 10] \\
+queries[j] &= 3 \\
+\end{array} $
+
+$ \begin{array}{l:l}
+  3 \oplus 3 = 0 & max = 0 \\
+  3 \oplus 7 = 4 & max = 4 \\
+  3 \oplus 15 = 12 & max = 12 \\
+  3 \oplus 10 = 9 & max = 12 \\
+\end{array} $
+
+## Function Description
+
+Complete the maxXor function in the editor below.
+It must return an array of integers,
+each representing the maximum xor value for each element `queries[j]`
+against all elements of `arr`.
+
+maxXor has the following parameter(s):
+
+- arr: an array of integers
+- queries: an array of integers to query
+
+## Input Format
+
+The first line contains an integer `n`, the size of the array `arr`.
+
+The second line contains `n` space-separated integers,
+`arr[i]` from $ 0 \leq i < n $.
+
+The third line contain `m`, the size of the array `queries`.
+
+Each of the next `m` lines contains an
+integer `queries[j]` where $ 0 \leq j < m $.
+
+## Constraints
+
+- $ 1 \leq n,m \leq 10^5 $
+- $ 0 \leq arr[i], queries[j] \leq 10^9 $
+
+## Output Format
+
+The output should contain `m` lines with each line representing output
+for the corresponding input of the testcase.
+
+## Sample Input 0
+
+```text
+3
+0 1 2
+3
+3
+7
+2
+```
+
+## Sample Output 0
+
+```text
+3
+7
+3
+```
+
+## Explanation 0
+
+$ arr = [0, 1, 2] $
+
+$ queries[0] = 3 $
+
+$ \begin{array}{l:l}
+  3 \oplus 0 = 3 & max = 3 \\
+  3 \oplus 1 = 2 & max = 3 \\
+  3 \oplus 2 = 1 & max = 3 \\
+\end{array} $
+
+$ queries[1] = 7 $
+
+$ \begin{array}{l:l}
+  7 \oplus 0 = 7 & max = 7 \\
+  7 \oplus 1 = 6 & max = 7 \\
+  7 \oplus 2 = 5 & max = 7 \\
+\end{array} $
+
+$ queries[2] = 2 $
+
+$ \begin{array}{l:l}
+  2 \oplus 0 = 2 & max = 3 \\
+  2 \oplus 1 = 3 & max = 3 \\
+  2 \oplus 2 = 0 & max = 3 \\
+\end{array} $
+
+## Sample Input 1
+
+```text
+5
+5 1 7 4 3
+2
+2
+0
+```
+
+## Sample Output 1
+
+```text
+7
+7
+```
+
+## Explanation 1
+
+$ arr = [5, 1, 7, 4, 3] $
+
+$ queries[0] = 2 $
+
+$ \begin{array}{l:l}
+  2 \oplus 5 = 7 & max = 7 \\
+  2 \oplus 1 = 3 & max = 7 \\
+  2 \oplus 7 = 5 & max = 7 \\
+  2 \oplus 4 = 7 & max = 7 \\
+  2 \oplus 3 = 3 & max = 7 \\
+\end{array} $
+
+$ queries[1] = 7 $
+
+$ \begin{array}{l:l}
+  0 \oplus 5 = 7 & max = 7 \\
+  0 \oplus 1 = 3 & max = 7 \\
+  0 \oplus 7 = 5 & max = 7 \\
+  0 \oplus 4 = 7 & max = 7 \\
+  0 \oplus 3 = 3 & max = 7 \\
+\end{array} $
+
+## Sample Input 2
+
+```text
+4
+1 3 5 7
+2
+17
+6
+```
+
+## Sample Output 2
+
+```text
+22
+7
+```
+
+## Explanation 2
+
+$ arr = [1, 2, 5, 7] $
+
+$ queries[0] = 17 $
+
+$ \begin{array}{l:l}
+  17 \oplus 16 = 16 & max = 16 \\
+  17 \oplus 18 = 18 & max = 18 \\
+  17 \oplus 20 = 20 & max = 20 \\
+  17 \oplus 22 = 22 & max = 22 \\
+\end{array} $
+
+$ queries[1] = 6 $
+
+$ \begin{array}{l:l}
+  6 \oplus 7 = 7 & max = 7 \\
+  6 \oplus 5 = 5 & max = 7 \\
+  6 \oplus 3 = 3 & max = 7 \\
+  6 \oplus 1 = 1 & max = 7 \\
+\end{array} $

src/hackerrank/interview_preparation_kit/miscellaneous/maximum_xor.py

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+# pylint: disable=line-too-long
+# @link Problem definition [[docs/hackerrank/interview_preparation_kit/miscellaneous/maximum-xor.md]] # noqa
+# pylint: enable=line-too-long
+
+def maxXor(arr: list[int], queries: list[int]) -> list[int]:
+    result = []
+
+    for j in queries:
+        maximum = 0
+        for x in arr:
+            maximum = max(maximum, j ^ x)
+        result.append(maximum)
+
+    return result

src/hackerrank/interview_preparation_kit/miscellaneous/maximum_xor.testcases.json

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+[
+  {
+    "title": "Sample Test case 0",
+    "arr": [0, 1, 2],
+    "queries": [3, 7, 2],
+    "expected": [3, 7, 3]
+  },
+  {
+    "title": "Sample Test case 1",
+    "arr": [5, 1, 7, 4, 3],
+    "queries": [2, 0],
+    "expected": [7, 7]
+  },
+  {
+    "title": "Sample Test case 2",
+    "arr": [1, 3, 5, 7],
+    "queries": [17, 6],
+    "expected": [22, 7]
+  }
+]

src/hackerrank/interview_preparation_kit/miscellaneous/maximum_xor_test.py

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+import unittest
+from pathlib import Path
+
+from ....lib.loader import loadTestCases
+from .maximum_xor import maxXor
+
+FILE_PATH = str(Path(__file__).resolve().parent)
+
+TEST_CASES = loadTestCases(
+    FILE_PATH + '/maximum_xor.testcases.json')
+
+
+class TestMaximumXor(unittest.TestCase):
+
+    def test_maximum_xor(self):
+
+        for _, _tt in enumerate(TEST_CASES):
+
+            self.assertEqual(
+                maxXor(_tt['arr'], _tt['queries']), _tt['expected'],
+                f"{_} | maxXor({_tt['arr']}, {_tt['queries']}) must be "
+                f"=> {_tt['expected']}")