[Swift]LeetCode1017. 负二进制转换 | Convert to Base -2
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Given a number N, return a string consisting of "0"s and "1"s that represents its value in base -2 (negative two).
The returned string must have no leading zeroes, unless the string is "0".
Example 1:
Input: 2 Output:
Example 2:
Input: 3 Output: Explantion: (-2) ^ 2 + (-2) ^ 1 + (-2) ^ 0 = 3
Example 3:
Input: 4 Output: Explantion: (-2) ^ 2 = 4
Note:
0 <= N <= 10^9
给出数字 N，返回由若干 "0" 和 "1"组成的字符串，该字符串为 N 的负二进制（base -2）表示。
除非字符串就是 "0"，否则返回的字符串中不能含有前导零。
示例 1：
输入：2 输出："110" 解释：(-2) ^ 2 + (-2) ^ 1 = 2
示例 2：
输入：3 输出："111" 解释：(-2) ^ 2 + (-2) ^ 1 + (-2) ^ 0 = 3
示例 3：
输入：4 输出："100" 解释：(-2) ^ 2 = 4
提示：
0 <= N <= 10^9
8ms
1 class Solution {
2 func baseNeg2(_ N: Int) -> String {
3 var num = N
4 var str = ""
5 var base = -2
6 while num < 0 || num >= 2 {
7 var q = Int(num / base)
8 if num < 0, num % base != 0 { q += 1 }
9 str = "\((num - q * base))\(str)"
10 num = q
11 }
12 if num != 0 {
13 str = "\(num)\(str)"
14 }
15 if str.isEmpty {
16 str = "0"
17 }
18 return str
19 }
20 }Runtime: 16 ms
Memory Usage: 18.9 MB
1 class Solution {
2 func baseNeg2(_ N: Int) -> String {
3 var N = N
4 var ans:String = String()
5 while(N != 0)
6 {
7 var r:Int = abs(N % 2)
8 if r != 0 { N -= 1}
9 var q:Int = N / -2
10 ans.append((r + 48).ASCII)
11 N = q
12 }
13 ans = String(ans.reversed())
14 if ans.isEmpty
15 {
16 ans.append("0")
17 }
18 return ans
19 }
20 }
21
22 //Int扩展
23 extension Int
24 {
25 //Int转Character,ASCII值(定义大写为字符值)
26 var ASCII:Character
27 {
28 get {return Character(UnicodeScalar(self)!)}
29 }
30 }