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.
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| public class Solution {
public String addStrings(String num1, String num2) {
char[] x = new StringBuilder(num1).reverse().toString().toCharArray();
char[] y = new StringBuilder(num2).reverse().toString().toCharArray();
char[] l, s;
if (num1.length() > num2.length()) {
l = x;
s = y;
} else {
l = y;
s = x;
}
StringBuilder sb = new StringBuilder();
int carry = 0;
int i = 0;
for (; i < l.length; i++) {
int a = l[i] - '0';
int b = (i >= s.length) ? 0 : s[i] - '0';
sb.append((a + b + carry) % 10);
if (a + b + carry >= 10) {
carry = 1;
} else {
carry = 0;
}
}
if (carry > 0) {
sb.append(1);
}
return sb.reverse().toString();
}
}
|