一.問題描述

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

For example,
a = "11"
b = "1"
Return "100".

二.我的解題思路

這道題也比較容易，直接按照規則計算即可。測試通過的程式如下：

class Solution {
public:
    string addBinary(string a, string b) {
        string ans; string tmp;
        int len_a = a.length(); int len_b = b.length();
        int len = len_a<len_b?len_a:len_b;
        int long_len = len_a>len_b?len_a:len_b;
        int i=1;int flag=0;
        if(a.length()==0) return b;
        if(b.length()==0) return a;
        while(i<=len){
            int plus_a = a[len_a-i]-'0';
            int plus_b = b[len_b-i]-'0';
            int res = plus_a + plus_b + flag;
            if(res>1) flag=1;
            else flag=0;
            res = res % 2;
            char curr = '0'+res;
            ans=curr +ans;
            i++;
        }
        if(len_a>len_b) tmp=a;
        else tmp=b;
        long_len = tmp.length();
        while(i<=tmp.length()){
            int plus_a = tmp[long_len-i]-'0';
            int res = plus_a  + flag;
            if(res>1) flag=1;
            else flag=0;
            res = res % 2;
            char curr = '0'+res;
            ans=curr +ans;
            i++;
        }
        if(flag==1)
        ans='1'+ans;
        return ans;
      
    }
};