LeetCode - 8. string conversion integer (Swift Language)

Atoi you to implement a function, it can convert a string to an integer.

First, the function will begin with a space character discard useless if necessary, until the find to the first non-space character so far.
When we find the first non-space character is a positive or negative number, the combination of the symbols as much as possible with consecutive numbers up later, as the sign of integer; if the first non-space character is figures, which directly after the continuous numeric characters are combined to form an integer.
In addition to the string after a valid integer part may also exist extra characters, these characters can be ignored, they should not affect a function.
Note: if the character string in the first non-space character is not a valid integer character string is empty or contains only white space character string, then you will not need to be a function of conversion.
In any case, if the function can not effectively convert, 0 is returned.
Description:
We assume that the size of the environment can store 32-bit signed integer, then the value range of [-231 231--1]. If the value exceeds this range, qing return INT_MAX (231 - 1) or INT_MIN (-231).

Example 1:

1 2	Input: "42" Output: 42

Example 2:

Input: "-42" 
Output: -42 
Explanation: a first non-blank character '-', it is a negative sign. 
     We will all digital consecutive negative number and later combined as much as possible, and finally get -42.

Example 3:

1
2
3

Input: "41931 with words" 
Output: 41931 
explanation: the digital conversion off '1', since it is not the next character is a number.

Example 4:

Input: "words and 987" 
Output: 0 
Explanation: a first non-blank character 'w', but it is not a positive number or negative number. 
     Therefore, the conversion can not be performed effectively.

Example 5:

Input: "-91283472332" 
Output: -2147483648 
explanation: the number "-91283472332" Over the range of 32-bit signed integer. 
     So return INT_MIN (-231).

Note:
Suppose we have an environment can store the 32-bit signed integer, then the value range of [-231 231--1]. Please According to this hypothesis, if integer overflow after reverse it returns 0.

Swift

class LeetCode8 {
    
    /* 检查用例
     "42"
     "+-2"
     "   -42"
     "words and 987"
     "0-1"
     */
    func myAtoi(_ str: String) -> Int {

        // intermediate transition value can only be nil type 
        var ISNUM:? Int = nil 
        // final gross 
        var Results: Int = 0 
        // whether negative? 
        isMinus var:? Bool = nil         for A in str {             the let S = String (A)             // NUM == nil whether the character has been             // isMinus == nil whether there had been operator             if isNum == nil && isMinus == && nil (S == "" || S == "-" || S == "+") {                 // operator                 // disguised space taken                 if s == "-" || s == "+" {                     isMinus = S == "-"                 }                 Continue             }             // Int able to turn indicates 0 ...
        














                let ii = isMinus ?? false ? -1 : 1
                results = isNum ?? 0
                results = results * 10 + i * ii
                isNum = results
                if results > Int32.max {
                    return Int(Int32.max)
                }
                if results < Int32.min {
                    return Int(Int32.min)
                }
            }else{
                break
            }
        }
        return results
    }
}

Original: Large Column LeetCode - 8. string conversion integer (Swift Language)

LeetCode - 8. string conversion integer (Swift Language)

Swift

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