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.
public class Solution {
public String addStrings(String num1, String num2) {
int i = num1.length() - 1, j = num2.length() - 1, carry = 0;
String res = "";
while (i >= 0 || j >= 0) {
if (i >= 0)
carry += num1.charAt(i--) - '0';
if (j >= 0)
carry += num2.charAt(j--) - '0';
res = Integer.toString(carry % 10) + res;
carry /= 10;
}
return carry != 0 ? "1"
