Leetcode：67. Add Binary（JAVA）

【问题描述】

Given two binary strings, return their sum (also a binary string).

For example,

a = 

"11"

b = 

"1"

Return 

"100"

.
【思路】

从string的最高位开始相加，设置进位。

【code】

public class Solution {
public String addBinary(String a, String b) {
if (a.length() < b.length()) {
return addBinary(b, a);
}
String sum = "";
int j = b.length() - 1;
int ca, cb, c = 0;
for (int i = a.length() - 1; i >= 0; i--) {
ca = a.charAt(i) - '0';
cb = 0;
if (j >= 0) {
cb = b.charAt(j) - '0';
j--;
}
int temp = ca + cb + c;
if (temp == 0) {
sum = '0' + sum;
c = 0;
}
if (temp == 1) {
sum = '1' + sum;
c = 0;
}
if (temp == 2) {
sum = '0' + sum;
c = 1;
}
if (temp == 3) {
sum = '1' + sum;
c = 1;
}
}
if (c == 1) {
sum = '1' + sum;
}
return sum;
}
}