LeetCode/StringToInteger at master · boh-prog/LeetCode · GitHub

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class Solution
{

   /**
    BELLOW IS MY SECOND ATTEMPT ON THIS PROBLEM
 **/

    public int myAtoi(String s)
    {
        //instantiate final value   //instantiate start indx    //assume sign of integer is positive
        int val = 0;                int startIndx=0;             int sign = 1;

        //remove all white space at beginning and end of string
        s = s.trim();

         if(s.length() <= 1 &&  s.matches("^[0-9]")) {return s.charAt(0)-'0';}
         else if(s.length() <= 1 &&  !s.matches("^[0-9]")) return 0;

        else
        {
            //check for sign at start of numeric value
            if(s.charAt(startIndx) == '-')
            {
                sign = -1; startIndx =1;
            }
            else if(s.charAt(startIndx) == '+') startIndx = 1; //positive sign is the default, so move start indx

            //loop through string and get numeric values
            for(int i = startIndx; i<s.length(); i++)
            {

                //In case of non numeric value where return the current calculated "val"
                if( !(s.charAt(i) >= '0' && s.charAt(i) <='9') )
                {
                    return val * sign;
                }

                //check if Val is whithin range [-2^31, 2^31-1]


                if(val > Integer.MAX_VALUE/10)
                {
                    //Underflow
                    if(sign == -1) return Integer.MIN_VALUE;
                    //OverFlow
                    return Integer.MAX_VALUE;
                }

                else if( (val == Integer.MAX_VALUE/10))
                {
                     //OverFlow
                    if((sign == 1) && !(s.charAt(i) >= '0' && s.charAt(i) <='7')) return Integer.MAX_VALUE;
                     //Underflow
                    if((sign == -1) && !(s.charAt(i) >= '0' && s.charAt(i) <='8')) return Integer.MIN_VALUE;
                }

                //if character is numeric, convert to int and add to val
                val = (val * 10) + s.charAt(i) - '0';
            }

            return val * sign;
        }


 /**
 BELLOW IS MY FIRST ATTEMPT ON THIS PROBLEM

 **/

        //When string is single charac
//         if(s.length() == 1 &&  s.matches("^[0-9]")) {return s.charAt(0)-'0';}
//         else if(s.length() == 1 &&  !s.matches("^[0-9]")) return 0;
//         else
//         {
//             for(int i =0; i<s.length(); i++)
//             {
//                 //get character in string
//                 char c = s.charAt(i);

//                 if (c >= '0' && c <= '9')
//                 {

//                     if((val >= Integer.MAX_VALUE/10)  ||  (val >= Integer.MAX_VALUE/10 + 7 ) )  return Integer.MAX_VALUE;

//                     else if((val <= Integer.MIN_VALUE/10)  ||  (val <= Integer.MIN_VALUE/10 - 8)) return Integer.MIN_VALUE;


//                     //add next numeric value to val; Note, multiplying by 'sign' to keep the sign of the integer
//                     val = (val * 10) + sign * (c - '0');

//                 }


//                 //edge case for non numeric charac between characs
//                 else if (i>0 && (s.charAt(i-1)>='0' && s.charAt(i-1)<='9') ) break;

//                 //check on non numeric characs
//                 else if (!(c >= '0' && c <= '9'))
//                  {
//                         // System.out.println(c);
//                     //check for sign of numeric charac
//                         if( c == '-' && (s.charAt(i+1)!='+') )  //s.charAt(i+1) != '-'
//                         {
//                             sign = -1;  //convert sign to negative
//                             continue;
//                         }
//                         if( c == '+' && (s.charAt(i+1) != '-' ) )  continue; //|| s.charAt(i+1)!='+'


//                         //break loop if a non-Numeric charac is found before or inbetween numeric characters
//                         else if(c >= 'A' && c <= 'Z' || c >= 'a' && c <= 'z' || c != '\s') break;


//                  }

//                 //breaks loop after all first numeric values have been read
//                 else if ( (c >= '0' && c <= '9') && !(s.charAt(i+1)>='0' && s.charAt(i+1)<='9' ) )
//                 {
//                     break;
//                 }
//             }

//             return val;
//         }

    }
}