0067. Add Binary
https://leetcode.com/problems/add-binary
Description
Given two binary strings a
and b
, return their sum as a binary string.
Example 1:
**Input:** a = "11", b = "1"
**Output:** "100"
Example 2:
**Input:** a = "1010", b = "1011"
**Output:** "10101"
Constraints:
1 <= a.length, b.length <= 104
a
andb
consist only of'0'
or'1'
characters.Each string does not contain leading zeros except for the zero itself.
ac
StringBuilder reverse()
class Solution {
public String addBinary(String a, String b) {
// edge cases
if (a == null || b == null || a.length() == 0 && b.length() == 0) return "";
// add
StringBuilder sb = new StringBuilder();
int carry = 0;
int ia = a.length() - 1, ib = b.length() - 1;
while (ia >= 0 || ib >= 0 || carry != 0) {
int curr = 0;
curr += ia >= 0 ? a.charAt(ia--) - '0' : 0;
curr += ib >= 0 ? b.charAt(ib--) - '0' : 0;
curr += carry;
sb.append("" + (curr % 2));
carry = curr / 2;
}
return sb.reverse().toString();
}
}
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