[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， 数组中每个元素只存储一个数字。

你可以假设除了整数 0 之外，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

class Solution {
    func plusOne(_ digits: [Int]) -> [Int] {
        var addOne = digits     
        var current = digits.count - 1
        var carryOver = false        
        var num = digits[current]

        if (current < 0)  {
            return addOne
        }
        
        num = addOne[current] + 1
        if (num<10) {
            addOne[current] = num
            return addOne
        } else {
            carryOver = true
            addOne[current] = 0
            current = current - 1
            while (current>=0) && (carryOver==true) {
                num = addOne[current] + 1
                if (num<10) {
                    addOne[current] = num
                    return addOne
                } else {
                    carryOver = true
                    addOne[current] = 0
                    current = current - 1
                }
            }
        }
    
        //[9] - >[0] ==>[1,0]
        print("addOne: (addOne)")
        if (carryOver==true)  {
            addOne[0] = 0
            addOne.insert(1, at: 0) 
            /*
            if (addOne[0]<9) {      
               addOne[0] = addOne[0] + 1 
            } else {
                addOne[0] = 0
                addOne.insert(1, at: 0)  
            }*/
        } 
        print("--**addOne: (addOne)")
        return addOne
    }
}

---

12ms

class Solution {
    func plusOne(_ digits: [Int]) -> [Int] {
        var copy = [Int](), carry = 0, add = 1
        for i in stride(from: digits.count-1, through: 0, by: -1){
            if(((digits[i] + add + carry)) == 10){
                carry = 1
                copy.append(0)
            }
            else{
                copy.append(digits[i] + carry + add)
                carry = 0
            }
            add = 0
        }
        if(carry != 0){copy.append(carry)}
        return copy.reversed()
    }
}

---

12ms

class Solution {
    func plusOne(_ digits: [Int]) -> [Int] {
        //获取数组长度
        var len:Int = digits.count
        //参数digits是let定义,转成可变参数
        var arr:[Int] = digits
        //倒序遍历数组
        for i in (0..<digits.count).reversed()
        {
            //如果数组最后一位不是整数9,加一返回数组
            if arr[i]<9
            {
                arr[i]+=1
                return arr  
            }
            else
            {
                //如果数组最后一位是整数9，则变成整数0。
                arr[i] = 0
            }
        }
        //程序运行至此是全9的情况,需要在首位插入数字1
        arr.insert(1, at: 0)
        return arr
    }
}

---

16ms

class Solution {
    func plusOne(_ digits: [Int]) -> [Int] {
        var resultArray = [Int]()
        var pointer = digits.count - 1
        var checkIfAdded = false
        
        
        if digits.count == 1 {
            if digits[0] + 1 > 9 {
                return [1,0]
            } else {
                return [digits[0] + 1]
            }  
        }
        
        
        while pointer >= 0 {
            if checkIfAdded == false {
               if digits[pointer] + 1 > 9 {
                    resultArray.insert(0, at: 0)
                    pointer -= 1
                } else {
                    resultArray.insert(digits[pointer] + 1, at: 0)
                    checkIfAdded = true
                    pointer -= 1
                }  
            } else {
                resultArray.insert(digits[pointer], at: 0)
                pointer -= 1
            } 
        }
        
        if resultArray[0] == 0 {
            resultArray.insert(1, at: 0)
        }
        
        return resultArray

    }
}

---

20ms

class Solution {
    func plusOne(_ digits: [Int]) -> [Int] {
        var carry : Int = 1
        var returnArray = digits
        
        for index in stride(from:digits.count - 1 , to: -1, by: -1){
            let value = (digits[index] + carry) % 10
            carry = (digits[index] + carry) / 10
            returnArray[index] = value
        }
        if carry == 1 {
            returnArray.insert(1 ,at:0)
        }
        return returnArray
    }
}