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415. add strings

admin 11月 15, 2020 0

Given two non-negative integers num1 and num2 represented as string, return the sum of num1 and num2.

Note:

The length of both num1 and num2 is < 5100.
Both num1 and num2 contains only digits 0-9.
Both num1 and num2 does not contain any leading zero.
You must not use any built-in BigInteger library or convert the inputs to integer directly.

class  {
    public String addStrings(String num1, String num2) {
        int i = num1.length() - 1;
       int j = num2.length() - 1;
      String s = "";
       int c = 0;
      while (i >= 0 || j >= 0 || c > 0) {
            c += i >= 0?num1.charAt(i--) - '0' : 0;
           c += j >= 0?num2.charAt(j--) - '0' : 0;
           s = c % 10 + s;
          c /= 10;
     }
        return s;
    }
}