[Swift]LeetCode66. 加一 | Plus One

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Given a non-empty array of digits representing a non-negative integer, plus one to the integer.

The digits are stored such that the most significant digit is at the head of the list, and each element in the array contain a single digit.

You may assume the integer does not contain any leading zero, except the number 0 itself.

Example 1:

Input: [1,2,3]
Output: [1,2,4]
Explanation: The array represents the integer 123.

Example 2:

Input: [4,3,2,1]
Output: [4,3,2,2]
Explanation: The array represents the integer 4321.

---

给定一个由整数组成的非空数组所表示的非负整数，在该数的基础上加一。

最高位数字存放在数组的首位， 数组中每一个元素只存储一个数字。

你能够假设除了整数 0 以外，这个整数不会以零开头。

示例 1:

输入: [1,2,3]
输出: [1,2,4]
解释: 输入数组表示数字 123。

示例 2:

输入: [4,3,2,1]
输出: [4,3,2,2]
解释: 输入数组表示数字 4321。

---

8ms

 1 class Solution {
 2     func plusOne(_ digits: [Int]) -> [Int] {
 3         var addOne = digits     
 4         var current = digits.count - 1
 5         var carryOver = false        
 6         var num = digits[current]
 7 
 8         if (current < 0)  {
 9             return addOne
10         }
11         
12         num = addOne[current] + 1
13         if (num<10) {
14             addOne[current] = num
15             return addOne
16         } else {
17             carryOver = true
18             addOne[current] = 0
19             current = current - 1
20             while (current>=0) && (carryOver==true) {
21                 num = addOne[current] + 1
22                 if (num<10) {
23                     addOne[current] = num
24                     return addOne
25                 } else {
26                     carryOver = true
27                     addOne[current] = 0
28                     current = current - 1
29                 }
30             }
31         }
32     
33         //[9] - >[0] ==>[1,0]
34         print("addOne: \(addOne)")
35         if (carryOver==true)  {
36             addOne[0] = 0
37             addOne.insert(1, at: 0) 
38             /*
39             if (addOne[0]<9) {      
40                addOne[0] = addOne[0] + 1 
41             } else {
42                 addOne[0] = 0
43                 addOne.insert(1, at: 0)  
44             }*/
45         } 
46         print("--**addOne: \(addOne)")
47         return addOne
48     }
49 }

---

12ms

 1 class Solution {
 2     func plusOne(_ digits: [Int]) -> [Int] {
 3         var copy = [Int](), carry = 0, add = 1
 4         for i in stride(from: digits.count-1, through: 0, by: -1){
 5             if(((digits[i] + add + carry)) == 10){
 6                 carry = 1
 7                 copy.append(0)
 8             }
 9             else{
10                 copy.append(digits[i] + carry + add)
11                 carry = 0
12             }
13             add = 0
14         }
15         if(carry != 0){copy.append(carry)}
16         return copy.reversed()
17     }
18 }

---

12ms

 1 class Solution {
 2     func plusOne(_ digits: [Int]) -> [Int] {
 3         //获取数组长度
 4         var len:Int = digits.count
 5         //参数digits是let定义,转成可变参数
 6         var arr:[Int] = digits
 7         //倒序遍历数组
 8         for i in (0..<digits.count).reversed()
 9         {
10             //若是数组最后一位不是整数9,加一返回数组
11             if arr[i]<9
12             {
13                 arr[i]+=1
14                 return arr  
15             }
16             else
17             {
18                 //若是数组最后一位是整数9，则变成整数0。
19                 arr[i] = 0
20             }
21         }
22         //程序运行至此是全9的状况,须要在首位插入数字1
23         arr.insert(1, at: 0)
24         return arr
25     }
26 }

---

16ms

 1 class Solution {
 2     func plusOne(_ digits: [Int]) -> [Int] {
 3         var resultArray = [Int]()
 4         var pointer = digits.count - 1
 5         var checkIfAdded = false
 6         
 7         
 8         if digits.count == 1 {
 9             if digits[0] + 1 > 9 {
10                 return [1,0]
11             } else {
12                 return [digits[0] + 1]
13             }  
14         }
15         
16         
17         while pointer >= 0 {
18             if checkIfAdded == false {
19                if digits[pointer] + 1 > 9 {
20                     resultArray.insert(0, at: 0)
21                     pointer -= 1
22                 } else {
23                     resultArray.insert(digits[pointer] + 1, at: 0)
24                     checkIfAdded = true
25                     pointer -= 1
26                 }  
27             } else {
28                 resultArray.insert(digits[pointer], at: 0)
29                 pointer -= 1
30             } 
31         }
32         
33         if resultArray[0] == 0 {
34             resultArray.insert(1, at: 0)
35         }
36         
37         return resultArray
38 
39     }
40 }

---

20ms

 1 class Solution {
 2     func plusOne(_ digits: [Int]) -> [Int] {
 3         var carry : Int = 1
 4         var returnArray = digits
 5         
 6         for index in stride(from:digits.count - 1 , to: -1, by: -1){
 7             let value = (digits[index] + carry) % 10
 8             carry = (digits[index] + carry) / 10
 9             returnArray[index] = value
10         }
11         if carry == 1 {
12             returnArray.insert(1 ,at:0)
13         }
14         return returnArray
15     }
16 }