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Tested Python solution for LeetCode 954 with 30 pytest cases. Generate a practice environment with lcpy.
lcpy gen -n 954 # by problem number
lcpy gen -s array_of_doubled_pairs # by problem name
arr, return true if it is possible to reorder arr such that arr[2 * i + 1] = 2 * arr[2 * i] for every 0 <= i < len(arr) / 2, or false otherwise.
Input: arr = [3,1,3,6]
Output: false
Input: arr = [2,1,2,6]
Output: false
Input: arr = [4,-2,2,-4]
Output: true
Explanation: We can take two groups, [-2,-4] and [2,4] to form [-2,-4,2,4] or [2,4,-2,-4].
from collections import Counter
class Solution:
# Time: O(n log n)
# Space: O(n)
def can_reorder_doubled(self, arr: list[int]) -> bool:
counts = Counter(arr)
for value in sorted(counts, key=abs):
need = counts[value]
if need == 0:
continue
if need > counts[2 * value]:
return False
counts[value] = 0
counts[2 * value] -= need
return True
| Time | Space |
|---|---|
| O(n log n) | O(n) |