Microsoft algorithm 100 questions 20 string to integer atoi

Question 20th:
Title: Enter a String representing an integer to convert the string to an integer and output.
For example, the input string "345", the output integer 345

Idea: Atoi is mainly concerned with the calibration and boundary processing of the input, as well as the processing of positive and negative symbols.

1  PackageCom.rui.microsoft;2 3  Public classTest20_string2int {4 5      Public Static voidMain (string[] args) {6         intsum = Test20_string2int.convert ("2147483648");7 System.out.println (sum);8     }9     Ten      Public Static intconvert (String input) { One         //remove prefix and suffix empty string Ainput =Input.trim (); -         //check null or empty string -         if(NULL= = Input | | Input.equals (""))return0; the          -         BooleanIsnegtive =false; -         //Check the start position -         intStart = 0; +         if('-' = =Input.charat (start)) { -Isnegtive =true; +start++; A}Else if(' + ' = =Input.charat (start)) { atIsnegtive =false; -start++; -         } -          -         intLength =input.length (); -         Longsum = 0; in          -          for(inti = start;i < length; i++){ to             Charc =Input.charat (i); +             if(!isdigit (c))return0; -             intTMP = C-' 0 '; thesum = sum*10 +tmp; *         } $         Panax Notoginseng         if(isnegtive) { -sum =-sum; the             returnSum<integer.min_value? Integer.min_value: (int) sum; +}Else{ A             returnSum>integer.max_value? Integer.max_value: (int) sum; the         } +          -     } $      $     Private Static BooleanIsDigit (Charc) { -         returnc>=48 && c<=57; -     } the  -}

Microsoft algorithm 100 questions 20 string to integer atoi