Difficulty: Easy
Given two binary strings, return their sum (also a binary string).
The input strings are both non-empty and contains only characters 1 or 0.
Example 1:
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Input: a = "11", b = "1"
Output: "100"
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Example 2:
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Input: a = "1010", b = "1011"
Output: "10101"
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Solution
Language: Java
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class {
public String addBinary(String a, String b) {
if (a == null || b == null) {
return "";
}
if (a.length() == 0) {
return b;
}
if (b.length() == 0) {
return a;
}
int i = a.length() - 1;
int j = b.length() - 1;
StringBuilder sb = new StringBuilder();
int carry = 0;
int cur = 0;
while (i >= 0 || j >= 0) {
cur = (i < 0 ? 0 : (a.charAt(i--) - '0')) +
(j < 0 ? 0 : (b.charAt(j--) - '0')) +
carry;
sb.append(cur % 2);
carry = cur / 2;
}
if (carry > 0) {
sb.append(1);
}
sb.reverse();
return sb.toString();
}
}
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