954. Array of Doubled Pairs

Given an array of integers A with even length, return true if and only if it is possible to reorder it such that A[2 * i + 1] = 2 * A[2 * i] for every 0 <= i < len(A) / 2.

Example 1:

Input: A = [3,1,3,6]
Output: false

Example 2:

Input: A = [2,1,2,6]
Output: false

Example 3:

Input: A = [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].

Example 4:

Input: A = [1,2,4,16,8,4]
Output: false

Constraints:

• 0 <= A.length <= 3 * 104
• A.length is even.
• -105 <= A[i] <= 105

# @lc code=start
using LeetCode

# add your code here:
function can_reorder_doubled(arr::Vector{Int})::Bool
    cnt = counter(arr)
    for a in sort!(arr; by=abs)
        cnt[a] == 0 && continue
        cnt[2a] == 0 && return false
        cnt[2a] -= 1
        cnt[a] -= 1
    end
    return true
end
# @lc code=end

can_reorder_doubled (generic function with 1 method)

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