1、前言

2、思路

做法跟十进制加法差不多

3、代码

class Solution {
    public String addBinary(String a, String b) {
        int m = a.length(), n = b.length();
        StringBuilder builder = new StringBuilder();
        int te = 0;
        int i = m - 1, j = n - 1;
        for(; i >= 0 && j >= 0; i--, j--){
            int aNum = a.charAt(i) - '0', bNum = b.charAt(j) - '0';
            int sum = aNum + bNum + te;
            int num = sum % 2;
            te = sum / 2;
            builder.insert(0, num);
        }
        while(i >= 0){
            int sum = a.charAt(i--) - '0' + te;
            te = sum / 2;
            builder.insert(0, sum % 2);
        }

        while(j >= 0){
            int sum = b.charAt(j--) - '0' + te;
            te = sum / 2;
            builder.insert(0, sum % 2);
        }

        while(te > 0){
            builder.insert(0, te % 2);
            te = te / 2;
        }
        return builder.toString();
    }
}