Add Binary
出处
Given two binary strings, return their sum (also a binary string).
For example,
a = "11"
b = "1"
Return "100".
Solution
'1'-'0' = 1.
Complexity
时间复杂度 O(n),空间复杂度 O(1);
Code
public class Solution {
public String addBinary(String a, String b) {
StringBuffer res = new StringBuffer();
int N = a.length(), M = b.length();
int i = N - 1, j = M - 1;
int carry = 0;
while (i>=0 || j>=0) {
int sum = carry;
if (i >= 0) sum += a.charAt(i--) - '0';
if (j >= 0) sum += b.charAt(j--) - '0';
carry = sum / 2;
res.insert(0,String.valueOf(sum % 2));
}
if (carry == 1) res.insert(0,'1');
return res.toString();
}
}