LeetCode in Kotlin

1009. Complement of Base 10 Integer

Easy

The complement of an integer is the integer you get when you flip all the 0’s to 1’s and all the 1’s to 0’s in its binary representation.

• For example, The integer 5 is "101" in binary and its complement is "010" which is the integer 2.

Given an integer n, return its complement.

Example 1:

Input: n = 5

Output: 2

Explanation: 5 is “101” in binary, with complement “010” in binary, which is 2 in base-10.

Example 2:

Input: n = 7

Output: 0

Explanation: 7 is “111” in binary, with complement “000” in binary, which is 0 in base-10.

Example 3:

Input: n = 10

Output: 5

Explanation: 10 is “1010” in binary, with complement “0101” in binary, which is 5 in base-10.

Constraints:

• 0 <= n < 109

Note: This question is the same as 476: https://leetcode.com/problems/number-complement/

Solution

import kotlin.math.pow

@Suppress("NAME_SHADOWING")
class Solution {
    fun bitwiseComplement(n: Int): Int {
        var n = n
        if (n == 0) {
            return 1
        }
        val list: MutableList<Int> = ArrayList()
        while (n != 0) {
            list.add(n and 1)
            n = n shr 1
        }
        var result = 0
        var exp = list.size - 1
        for (i in list.indices.reversed()) {
            if (list[i] == 0) {
                result += 2.0.pow(exp.toDouble()).toInt()
            }
            exp--
        }
        return result
    }
}

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