415. Two strings added add Strings

Given non-negative Numbersnum1andnum2Represented as String, return the sum ofnum1andnum2.

Note:

2. the length of Both num1  and num2  is < 5100.
4. both num1  and num2  contains only Digits 0-9 .
6. Both num1 and num2 does not contain any leading zero.
8. You must no built-in BigInteger library or convert the inputs to integer directly.

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public class Solution {
    
   

   
 public string AddStrings(string num1, string num2) {
    
   

   
 string s = "";
    
   

   
 int maxLength = Math.Max(num1.Length, num2.Length);
    
   

   
 num1 = num1.PadLeft(maxLength, ‘0‘);
    
   

   
 num2 = num2.PadLeft(maxLength, ‘0‘);
    
   

   

    
   

   
 int carry = 0;
    
   

   
 int digit = 0;
    
   

   
 int i = maxLength - 1;
    
   

   
 while (i >= 0 || carry>0)
    
   

   
 {
    
   

   
 digit = carry;
    
   

   
 if (i >= 0)
    
   

   
 {
    
   

   
 digit += ((int)num1[i] - 48) + ((int)num2[i] - 48);
    
   

   
 }
    
   

   
 if (digit >= 10)
    
   

   
 {
    
   

   
 carry = digit / 10;
    
   

   
 }
    
   

   
 else
    
   

   
 {
    
   

   
 carry = 0;
    
   

   
 }
    
   

   
 s = (digit % 10).ToString() + s;
    
   

   
 i--;
    
   

   
 }
    
   

   
 return s;
    
   

   
 }
    
   

   
}
   
  

From for notes (Wiz)

415. Two strings added add Strings