Easy
Given two non-negative integers, num1
and num2
represented as string, return the sum of num1
and num2
as a string.
You must solve the problem without using any built-in library for handling large integers (such as BigInteger
). You must also not convert the inputs to integers directly.
Example 1:
Input: num1 = “11”, num2 = “123”
Output: “134”
Example 2:
Input: num1 = “456”, num2 = “77”
Output: “533”
Example 3:
Input: num1 = “0”, num2 = “0”
Output: “0”
Constraints:
1 <= num1.length, num2.length <= 104
num1
and num2
consist of only digits.num1
and num2
don’t have any leading zeros except for the zero itself.public class Solution {
public String addStrings(String num1, String num2) {
StringBuilder result = new StringBuilder();
int carry = 0;
for (int i = num1.length() - 1, j = num2.length() - 1;
i >= 0 || j >= 0 || carry != 0;
i--, j--) {
int sum = carry;
if (i >= 0) {
sum += Character.digit(num1.charAt(i), 10);
}
if (j >= 0) {
sum += Character.digit(num2.charAt(j), 10);
}
carry = sum / 10;
result.append(sum % 10);
}
return result.reverse().toString();
}
}