String to Integer: strings turned to plastic

[Question:]

Hint:carefully consider all possible input cases. If you are want a challenge, please don't be below and ask yourself what are input possible.

Notes:it is intended for this problem to be specified vaguely (ie, no given input specs). You are are responsible to gather all of the input requirements up front.

Requirements for Atoi:

The function A-discards as many whitespace characters as necessary until the ' the ' non-whitespace is character. Then, starting from this character, takes a optional initial plus or minus sign followed by as many numerical as P Ossible, and interprets them as a numerical value.

The string can contain additional characters after those that form the integral number, which are ignored and have no Effe CT on the behavior's this function.

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If the sequence of non-whitespace characters in Str are not a valid integral number, or if no such sequence Cause either str is empty or it contains only whitespace characters, no conversion is performed.

If No valid conversion could are performed, a zero value is returned. If the correct value is out of the range of representable values, Int_max (2147483647) or int_min ( -2147483648) is Returne D.

[Analysis:]① string is empty or empty string, return 0;② ignore the space before and after the string; ③ the first character is ' + ' or '-' remember it first, then read down, and if you read a number, start working with numbers, and if you have other special characters, stop reading and return the results; ④ processing, if you convert Value exceeds the range of type int, the maximum or minimum value of int is returned.
[Solution:]

public class Solution {private final static int int_max = 2147483647;  
     
    Private final static int int_min =-2147483648;  
             
        public int atoi (String str) {int i = 0, flag = 1;//flag is a positive or negative marker long result = 0;//may be long after conversion  
             
        if (str = NULL | | str.length () = = 0) {return 0;//Step 1}  
             
        char[] ch = Str.trim (). ToCharArray (); if (Ch.length = = 0) {return 0;//Step 2} if (ch[i] = = ' + ' | | | ch[i] = = ' -') {flag = ch[i++] = = ' + '? 1:-1;//Step 3} while (I < ch.length &&am P Ch[i] >= ' 0 ' && ch[i] <= ' 9 ') {result = result * + (ch[i++]-' 0 ');//' 0 ' to ' 9 ' askii code is 48~5 7 if (Result * Flag < Int_min | |-result * flag > Int_max) {return result * flag ; Int_min? Int_min:int_max;  
       Step 4     } return (int) result * FLAG;  
    public static void Main (string[] args) {System.out.println (New Solution (). Atoi ("999")); }  
}