[Swift]LeetCode67.二进制求和|AddBinary

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Given two binary strings, return their sum (also a binary string).

The input strings are both non-empty and contains only characters 1 or 0.

Example 1:

Input: a = "11", b = "1"
Output: "100"

Example 2:

Input: a = "1010", b = "1011"
Output: "10101"

给定两个二进制字符串，返回他们的和（用二进制表示）。

输入为非空字符串且只包含数字 1 和 0。

示例 1:

输入: a = "11", b = "1"
输出: "100"

示例 2:

输入: a = "1010", b = "1011"
输出: "10101"

12ms

 1 class Solution {
 2     func addBinary(_ a: String, _ b: String) -> String {
 3         let charsA = Array(a)
 4         let charsB = Array(b)
 5         var ans = ""
 6         var m = charsA.count - 1
 7         var n = charsB.count - 1
 8         var carry = false
 9         while m >= 0 && n >= 0 {
10             if charsA[m] == "1" && charsB[n] == "1" {
11                 if carry {
12                     ans = "1" + ans
13                 } else {
14                     ans = "0" + ans
15                 }
16                 carry = true
17             } else if charsA[m] == "1" || charsB[n] == "1" {
18                 if carry {
19                     ans = "0"  + ans
20                     carry = true
21                 } else {
22                     ans = "1" + ans
23                     carry = false
24                 }
25             } else {
26                 if carry {
27                     ans = "1" + ans
28                 } else {
29                     ans = "0" + ans
30                 }
31                 carry = false
32             }
33             m -= 1
34             n -= 1
35         }
36         while m >= 0 {
37             if charsA[m] == "1" {
38                 if carry {
39                     ans = "0" + ans
40                 } else {
41                     ans = "1" + ans
42                 }
43             } else {
44                 if carry {
45                     ans = "1" + ans
46                 } else {
47                     ans = "0" + ans
48                 }
49                 carry = false
50             }
51             m = m - 1
52         }
53         while n >= 0 {
54             if charsB[n] == "1" {
55                 if carry {
56                     ans = "0" + ans
57                 } else {
58                     ans = "1" + ans
59                 }
60             } else {
61                 if carry {
62                     ans = "1" + ans
63                 } else {
64                     ans = "0" + ans
65                 }
66                 carry = false
67             }
68              n -= 1
69         }
70         if carry {
71             ans = "1" + ans
72         }
73         return ans
74     }
75 }

16ms

 1 class Solution {
 2     func addBinary(_ a: String, _ b: String) -> String {
 3         var lhs: [Character] = a.reversed()
 4         var rhs: [Character] = b.reversed()
 5         // zero padding
 6         if lhs.count < rhs.count {
 7             lhs.append(contentsOf: String(repeating: "0", count: rhs.count - lhs.count))
 8         }
 9         else if rhs.count < lhs.count {
10             rhs.append(contentsOf: String(repeating: "0", count: lhs.count - rhs.count))
11         }
12         // adding
13         let len = lhs.count
14         var step = 0
15         var result = ""
16         for i in 0..<len {
17             switch (lhs[i], rhs[i], step) {
18             case ("0", "0", 0):
19                 result.append("0")
20                 step = 0
21             case ("0", "0", 1):
22                 fallthrough
23             case ("0", "1", 0):
24                 fallthrough
25             case ("1", "0", 0):
26                 result.append("1")
27                 step = 0
28             case ("1", "1", 0):
29                 fallthrough
30             case ("1", "0", 1):
31                 fallthrough
32             case ("0", "1", 1):
33                 result.append("0")
34                 step = 1
35             case ("1", "1", 1):
36                 result.append("1")
37                 step = 1
38             default: fatalError()
39             }
40         }
41         if step == 1 {
42             result.append("1")
43         }
44         while result.last == "0" {
45             result.removeLast()
46         }
47         if result == "" {
48             result = "0"
49         }
50         return String(result.reversed())
51     }
52 }

20ms

 1 class Solution {
 2     func StringToNum(_ s: String) -> Int {
 3         var num = 0
 4         for c in s.characters
 5         {
 6             var n = 0
 7             if (c == "1") {
 8                 n = 1
 9             }
10             num = num * 2 + n
11         }
12         return num
13     }
14     
15     func NumToString(_ num_: Int) -> String {
16         if num_ == 0 {
17             return "0"            
18         }
19     
20         var num = num_
21         var str = ""
22         while num > 0 {
23             var n = num % 2
24             num /= 2
25             var s: String
26             if n == 0 {
27                 s = "0"
28             }
29             else {
30                 s = "1"
31             }
32             str = s + str
33         }
34         
35         return str
36     }
37     
38     func StringToArr(_ s: String) -> [Int] {
39         var nums: [Int] = [Int](repeating: 0, count:s.count)
40         var idx = nums.count - 1
41         for c in s.characters
42         {
43             var n = 0
44             if (c == "1") {
45                 n = 1
46             }
47             nums[idx] = n
48             idx -= 1
49         }
50         return nums
51     }
52     
53     func ArrToString(_ nums: [Int]) -> String {
54 
55         var str = ""
56         for i in 0...nums.count - 1 {
57             if (!(i == nums.count - 1 && nums[i] == 0)) {
58                 str = String(nums[i]) + str
59             }
60         }
61         
62         return str
63     }
64     
65     func ArrAdd(_ a: [Int], _ b: [Int]) -> [Int] {
66         var c_cnt = max(a.count, b.count) + 1;
67         var c: [Int] = [Int](repeating: 0, count: c_cnt)
68         var up = 0
69         for i in 0...c_cnt - 1 {
70             var sum = up
71             if (i < a.count) {
72                 sum += a[i]
73             }
74             if (i < b.count) {
75                 sum += b[i]
76             }
77             if sum >= 2 {
78                 sum -= 2
79                 up = 1
80             }
81             else {
82                 up = 0
83             }
84             c[i] = sum            
85         }
86         return c
87     }
88     
89     func addBinary(_ a: String, _ b: String) -> String {
90          var aa = StringToArr(a)
91          var bb = StringToArr(b)
92         // print(aa,bb)
93          var cc = ArrAdd(aa,bb)
94          var c = ArrToString(cc)
95          print(c)
96      
97         return c
98     }
99 }

24ms

 1 class Solution {
 2     func addBinary(_ a: String, _ b: String) -> String {
 3         var sum = 0, carry = 0, res = ""
 4         let aChars = Array(a.characters), bChars = Array(b.characters)
 5         var i = aChars.count - 1, j = bChars.count - 1
 6         
 7         while i >= 0 || j >= 0 || carry > 0 {
 8             sum = carry
 9             if i >= 0 {
10                 sum += Int(String(aChars[i]))!
11                 i -= 1
12             }
13             if j >= 0 {
14                 sum += Int(String(bChars[j]))!
15                 j -= 1
16             }
17             carry = sum / 2
18             sum = sum % 2
19             res = String(sum) + res
20         }
21         
22         return res
23     }
24 }

28ms

 1 class Solution {
 2     //从最低位加到最高位，当前位相加结果是%2，进位是/2，
 3     //记得处理每一次的进位和最后一次的进位，最后反向输出字符。
 4     func addBinary(_ a: String, _ b: String) -> String {
 5         //存储字符的输出变量
 6         var str:String = String()
 7         //获取a的字符数量
 8         var i:Int = a.count-1
 9         //获取b的字符数量
10         var j:Int = b.count-1
11         //进位标志
12         var carry:Int = 0
13         while(i>=0 || j>=0)
14         {
15             var sum:Int = carry
16             if i>=0
17             {
18                 //获取该索引的字符
19                 var char:Character = a[a.index(a.startIndex, offsetBy: i)]
20                 //将字符转换成整数
21                 for code in char.unicodeScalars {
22                     //字符 0 的ASCII码为48
23                     sum += (Int(code.value) - 48)
24                 }
25                 //自减
26                 i-=1
27             }
28             if j>=0
29             {
30                 //获取该索引的字符
31                 var char:Character = b[b.index(b.startIndex, offsetBy: j)]
32                 //将字符转换成整数
33                 for code in char.unicodeScalars {
34                     //字符 0 的ASCII码为48
35                     sum += (Int(code.value) - 48)
36                 }                
37                 //自减
38                 j-=1
39             }
40             //转换为临时字符串
41             var temp = String(sum % 2)
42             //追加到字符串末尾
43             str.append(temp[temp.startIndex])     
44             carry = sum/2
45         }
46         if carry != 0
47         {
48              //转换为临时字符串
49              var  temp = String(carry)
50             //追加到字符串末尾
51              str.append(temp[temp.startIndex])
52         }
53         //返回逆序字符串
54         return String(str.reversed())
55     }
56 }

40ms

 1 class Solution {
 2     func addBinary(_ a: String, _ b: String) -> String {
 3         var arr1 = [Int]()
 4         for c in a {
 5             arr1.append(Int(String.init(c))!)
 6         }
 7         var arr2 = [Int]()
 8         for c in b.unicodeScalars {
 9             arr2.append(Int(String.init(c))!)
10         }
11         if arr1.count > arr2.count {
12             return addBinaryWithArr(arr1, short: arr2)
13         }
14         return addBinaryWithArr(arr2, short: arr1)
15     }
16     
17     func addBinaryWithArr(_ long:[Int], short:[Int]) -> String {
18         
19         func toString(_ array:[Int]) -> String {
20             var str = ""
21             for num in array {
22                 str += "\(num)"
23             }
24             return str
25         }
26         
27         var long = long
28         var target = 0
29         var initIndex = long.count - short.count
30         var i = short.count-1
31         while i >= 0 {
32             let temp = long[initIndex + i] + short[i] + target
33             if temp > 1 {
34                 /// 有进位
35                 long[initIndex + i] = temp - 2
36                 target = 1
37             }else{
38                 /// 无进位
39                 long[initIndex + i] = temp
40                 target = 0
41             }
42             i -= 1
43         }
44         
45         if target == 0 {
46             return toString(long)
47         }
48         
49         var j = initIndex - 1
50         while j >= 0 {
51             if long[j] == 0 {
52                 long[j] = 1
53                 return toString(long 
                       
                    
                     
                      



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