# 4.07.2023 [137. Single Number II]

Single number in an array of triples

4.07.2023

137. Single Number II medium
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Problem TLDR

Single number in an array of triples

Intuition

One simple approach it to count bits at each position.
Result will have a 1 when count % 3 != 0.

Approach

Let’s use fold.

Complexity

• Time complexity:
  O(n)

• Space complexity:
  O(1)

Code

fun singleNumber(nums: IntArray): Int =
//110
//110
//110
//001
//001
//001
//010
//010
//010
//100
//463
(0..31).fold(0) { res, bit ->
    res or ((nums.count { 0 != it and (1 shl bit) } % 3) shl bit)
}