Question
Given two binary strings, return their sum (also a binary string).
For example,
a = "11"
b = "1"
Return "100".
Stats
| Frequency | 4 |
| Difficulty | 2 |
| Adjusted Difficulty | 2 |
| Time to use | ---------- |
Ratings/Color = 1(white) 2(lime) 3(yellow) 4/5(red)
Analysis
This is an easy question. Pure coding.
There are some boundary issues during my first attempt. And special note to the trim() operation after “String.valueOf(ans)”, it’s easy to omit.
My code
public String addBinary(String a, String b) {
int m = a.length(), n = b.length();
char[] ans = new char[Math.max(m, n) + 1];
int p = m - 1, q = n - 1, r = ans.length - 1;
int carry = 0;
while (r >= 0) {
if (p >= 0)
ans[r] += a.charAt(p--) - '0';
if (q >= 0)
ans[r] += b.charAt(q--) - '0';
int temp = ans[r] + carry;
ans[r] = (char) (temp % 2 + '0');
carry = temp / 2;
r--;
}
if (ans[0] == '0')
ans[0] = ' ';
return String.valueOf(ans).trim();
}