【leetcode】Add Binary

Add Binary

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

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

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先补全字符串，从末尾开始加，每次计算当前位和进位即可

 1 class Solution {
 2 public:
 3     char addBit(char a,char b,char &c)
 4     {
 5         if(a==b&&a=='1')
 6         {
 7             char ret;
 8             ret=c;
 9             c='1';
10             return ret;
11         }
12         else if(a==b&&a=='0')
13         {
14             
15             if(c=='0')
16             {
17                 return '0';
18             }
19             else
20             {
21                 c='0';
22                 return '1';
23             }
24         }
25         else
26         {
27             if(c=='1')
28                return '0';
29             else
30                return '1';
31             
32         }
33     }
34     
35     string addBinary(string a, string b) {
36         
37         int na=a.length()-1;
38         int nb=b.length()-1;
39         
40         if(na!=nb)
41         {
42             string tmp(abs(na-nb),'0');
43             if(na>nb)
44                 b=tmp+b;
45             else
46                 a=tmp+a;
47         }
48         
49         int i=a.length()-1;
50         string result(a.length(), '1');
51         char c='0';
52         
53         while(i>=0)
54         {
55             result[i]=addBit(a[i],b[i],c);
56             i--;
57         }
58         if(c=='0')
59         {
60             return result;
61         }
62         else
63         {
64             return '1'+result;
65         }
66     }
67 };