Add Binary
https://leetcode.com/problems/add-binary/
Given two binary strings, return their sum (also a binary string).
For example,
a = "11"
b = "1"
Return "100".
算法
- 假设aLen表示string a的长度,那么它的第aLen - 1个元素表示的最低位;string b同
- 用一个flag记录来代表进位
代码
public class Solution {
public String addBinary(String a, String b) {
if (a == null || b == null) {
return "";
}
if (a.isEmpty()) {
return b;
}
if (b.isEmpty()) {
return a;
}
int s;
int flag = 0;
StringBuilder sb = new StringBuilder();
int i = a.length() - 1;
int j = b.length() - 1;
do {
if (i >= 0 && j >= 0) {
s = a.charAt(i--) - '0' + b.charAt(j--) - '0' + flag * 1;
} else if (i >= 0) {
s = a.charAt(i--) - '0' + flag * 1;
} else {
s = b.charAt(j--) - '0' + flag * 1;
}
flag = s / 2;
sb.append(s % 2);
} while (i >= 0 || j >= 0);
if (1 == flag) {
sb.append(1);
}
return sb.reverse().toString();
}
}