LeetCode in Kotlin

89. Gray Code

Medium

An n-bit gray code sequence is a sequence of 2n integers where:

Given an integer n, return any valid n-bit gray code sequence.

Example 1:

Input: n = 2

Output: [0,1,3,2]

Explanation: The binary representation of [0,1,3,2] is [00,01,11,10]. - 00 and 01 differ by one bit - 01 and 11 differ by one bit - 11 and 10 differ by one bit - 10 and 00 differ by one bit [0,2,3,1] is also a valid gray code sequence, whose binary representation is [00,10,11,01]. - 00 and 10 differ by one bit - 10 and 11 differ by one bit - 11 and 01 differ by one bit - 01 and 00 differ by one bit

Example 2:

Input: n = 1

Output: [0,1]

Constraints:

Solution

@Suppress("NAME_SHADOWING")
class Solution {
    fun grayCode(n: Int): List<Int> {
        var n = n
        var n1 = arrayOf(0)
        var shift = 1
        while (n > 0) {
            val temp = Array(n1.size * 2) { 0 }
            var pos = 0
            for (integer in n1) {
                temp[pos++] = integer
            }
            for (i in n1.indices.reversed()) {
                temp[pos++] = n1[i] or shift
            }
            n1 = temp
            shift = shift shl 1
            n--
        }
        return listOf(*n1)
    }
}