Add Binary
Given two binary strings, return their sum (also a binary string).
For example,
a = "11"
b = "1"
Return "100".
SOLUTION:
指针指到两个字符串的末尾，不断往前推进，用carry表示进位。用stringbuilder来记录结果。
使用insert(0, c)函数将加出的结果不断插入到STRINGBUILDER.
public class Solution {
public String addBinary(String a, String b) {
if (a == null || b == null) {
return null;
}
if (a.length() == 0) {
return b;
}
if (b.length() == 0) {
return a;
}
StringBuilder sb = new StringBuilder();
int p1 = a.length() - 1;
int p2 = b.length() - 1;
int carry = 0;
while (p1 >= 0 || p2 >= 0) {
int sum = carry;
if (p1 >= 0) {
sum += (a.charAt(p1) - '0');
}
if (p2 >= 0) {
sum += (b.charAt(p2) - '0');
}
char c = sum % 2 == 1 ? '1': '0';
sb.insert(0, c);
carry = sum / 2;
p1--;
p2--;
}
if (carry == 1) {
sb.insert(0, '1');
}
return sb.toString();
}
}
GITHUB CODE: