415 Add Strings
Problem:
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.
Solutions:
public class Solution {
public String addStrings(String num1, String num2) {
num1 = new StringBuilder(num1).reverse().toString();
num2 = new StringBuilder(num2).reverse().toString();
String result = "";
int carry = 0;
for (int i = 0; i < num1.length() || i < num2.length(); i ++) {
int c1 = 0;
int c2 = 0;
if (i < num1.length()) {
c1 = num1.charAt(i) - '0';
}
if (i < num2.length()) {
c2 = num2.charAt(i) - '0';
}
int sum = c1 + c2 + carry;
int digit = sum % 10;
carry = sum / 10;
result = digit + result;
}
if (carry != 0) {
result = carry + result;
}
return result;
}
}