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hashes/array_pairs_divisibility.py
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84
hashes/array_pairs_divisibility.py
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"""
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check-if-array-pairs-are-divisible-by-k
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Problem statement:
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Given an array of integers arr of even length n and an integer k.
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Divide the array into n / 2 pairs such that the sum of each pair is divisible by k.
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Return true If you can find a way to do that or false otherwise.
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Example 1:
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Input: arr = [1,2,3,4,5,10,6,7,8,9], k = 5
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Output: true
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Explanation: Pairs are (1,9),(2,8),(3,7),(4,6) and (5,10).
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Example 2:
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Input: arr = [1,2,3,4,5,6], k = 7
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Output: true
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Explanation: Pairs are (1,6),(2,5) and(3,4).
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Example 3:
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Input: arr = [1,2,3,4,5,6], k = 10
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Output: false
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Explanation: You can try all possible pairs.
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See that there is no way to divide arr into 3 pairs each with sum divisible by 10.
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Constraints:
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arr.length == n
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1 <= n <= 105
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n is even.
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-109 <= arr[i] <= 109
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1 <= k <= 105
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"""
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# Time complexity: O(n)
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# Space complexity: O(k)
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# Approach:
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# 1. Create a list of size k with all elements as 0.
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# 2. For each element in the array, increment the element at index i%k.
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# 3. If the element at index 0 is odd, return False.
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# 4. Check if the number of elements at index i and k-i are equal.
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# 5. If not, return False.
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# 6. If all the conditions are satisfied, return True.
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class Solution:
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def can_arrange(self, arr: list[int], input_num: int) -> bool:
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"""
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Function to check if array pairs are divisible by k
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:param arr: List of integers
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:param k: Integer
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:return: Boolean
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Example:
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>>> obj = Solution()
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>>> obj.can_arrange([1, 2, 3, 4, 5, 10, 6, 7, 8, 9], 5)
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True
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>>> obj.can_arrange([1, 2, 3, 4, 5, 6], 7)
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True
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"""
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sol_arr = [0 for i in range(input_num)]
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for i in arr:
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sol_arr[i % input_num] += 1
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if sol_arr[0] % 2 != 0:
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return False
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i, j = 1, input_num - 1
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while j > i:
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if sol_arr[i] == sol_arr[j]:
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j -= 1
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i += 1
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else:
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return False
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return True
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# Driver code
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if __name__ == "__main__":
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arr = [1, 2, 3, 4, 5, 10, 6, 7, 8, 9]
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input_num = 5
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s = Solution()
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print(s.can_arrange(arr, input_num)) # Output: True
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