[Swift]LeetCode1009. 十进制整数的补码 | Complement of Base 10 Integer

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Every non-negative integer N has a binary representation.  For example, 5 can be represented as "101" in binary, 11 as "1011" in binary, and so on.  Note that except for N = 0, there are no leading zeroes in any binary representation.

The complement of a binary representation is the number in binary you get when changing every 1 to a 0and 0 to a 1.  For example, the complement of "101" in binary is "010" in binary.

For a given number N in base-10, return the complement of it's binary representation as a base-10 integer.

Example 1:

Input: 5
Output: 2
Explanation: 5 is "101" in binary, with complement "010" in binary, which is 2 in base-10.

Example 2:

Input: 7
Output: 0
Explanation: 7 is "111" in binary, with complement "000" in binary, which is 0 in base-10.

Example 3:

Input: 10
Output: 5
Explanation: 10 is "1010" in binary, with complement "0101" in binary, which is 5 in base-10.

Note:

1. 0 <= N < 10^9

---

每个非负整数 N 都有其二进制表示。例如， 5 可以被表示为二进制 "101"，11 可以用二进制 "1011" 表示，依此类推。注意，除 N = 0 外，任何二进制表示中都不含前导零。

二进制的补码表示是将每个 1 改为 0 且每个 0 变为 1。例如，二进制数 "101" 的二进制补码为 "010"。

给定十进制数 N，返回其二进制表示的补码所对应的十进制整数。

示例 1：

输入：5
输出：2
解释：5 的二进制表示为 "101"，其二进制补码为 "010"，也就是十进制中的 2 。

示例 2：

输入：7
输出：0
解释：7 的二进制表示为 "111"，其二进制补码为 "000"，也就是十进制中的 0 。

示例 3：

输入：10
输出：5
解释：10 的二进制表示为 "1010"，其二进制补码为 "0101"，也就是十进制中的 5 。 

提示：

1. 0 <= N < 10^9

---

Runtime: 4 ms

Memory Usage: 19 MB

class Solution {
    func bitwiseComplement(_ N: Int) -> Int {
        var N = N
        var bits:[Int] = [Int]()
        repeat{
            bits.append(N % 2)
            N /= 2            
        }while(N != 0)
        for i in 0..<bits.count
        {
            bits[i] = 1 - bits[i]
        }
        var val:Int = 0
        var p:Int = 1
        for i in 0..<bits.count
        {
            val += p * bits[i]
            p *= 2
        } 
        return val        
    }
}

---

4ms

class Solution {
    func bitwiseComplement(_ N: Int) -> Int {
        var c = 1
        while c < N {
            c = (c << 1) | 1
        }
        return N ^ c        
    }
}

---

Runtime: 8 ms

Memory Usage: 18.9 MB

class Solution {
    func bitwiseComplement(_ N: Int) -> Int {
        var arrInt:[Int] = String(N,radix:2).map{Int(String($0))!}
        for i in 0..<arrInt.count
        {
            arrInt[i] = 1 - arrInt[i]         
        }
        return String(arrInt.map{Character(String($0))}).BinaryToDecimal()        
    }
}
extension String{
   func BinaryToDecimal() -> Int {    
       var sum:Int = 0
       for c in self.characters {
           if let number = Int(String(c))
           {
               sum = sum * 2 + number
           }        
       }
       return sum   
   }
}