67. Add Binary

Posted 2020-07-25 whl-hl

1. 问题描述

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

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

Tags: Math String

2. 解答思路

3. 代码

 1 #include <stack>
 2 #include <string>
 3 #include <cctype>
 4 using namespace std;
 5 class Solution {
 6 public:
 7     string addBinary(string a, string b){
 8         int aLen = a.size();
 9         int bLen = b.size();
10         if (0 == aLen)
11         {
12             return b;
13         }
14         if (0 == bLen)
15         {
16             return a;
17         }
18 
19         if (aLen >= bLen)
20         {
21             return add(a, b);
22         }
23         else
24         {
25             return add(b, a);
26         }
27     }
28 private:
29     string add(string a, string b)
30     {
31         int nTakeOver = 0;
32         int i = b.size()-1;
33         int j = a.size() - 1;
34         std::string sum = "";
35         std::string str_0 = "0";
36         std::string str_1 = "1";
37 
38         for (; i>=0; i--,j--)
39         {
40             int ta = a[j] - ‘0‘;
41             char tb = b[i] - ‘0‘;
42             int r = (ta + tb + nTakeOver) % 2;
43             nTakeOver = (ta + tb + nTakeOver) / 2;
44             if (r == 0)
45             {
46                 sum.insert(sum.begin(), str_0.begin(), str_0.end());
47             }
48             else
49             {                    
50                 sum.insert(sum.begin(), str_1.begin(), str_1.end());
51             }
52         }
53         if (j<0)
54         {
55             if (nTakeOver == 0)
56             {
57                 return sum;
58             }
59             else
60             {
61                 sum.insert(sum.begin(), str_1.begin(), str_1.end());
62                 return sum;
63             }
64         }
65         else
66         {
67             while (j>=0)
68             {
69                 int ta = a[j] - ‘0‘;
70                 int r = (ta + nTakeOver) % 2;
71                 nTakeOver = (ta + nTakeOver) / 2;
72                 if (r == 0)
73                 {
74                     sum.insert(sum.begin(), str_0.begin(), str_0.end());
75                 }
76                 else
77                 {                    
78                     sum.insert(sum.begin(), str_1.begin(), str_1.end());
79                 }
80                 j--;
81             }
82             if (nTakeOver == 0)
83             {
84                 return sum;
85             }
86             else
87             {
88                 sum.insert(sum.begin(), str_1.begin(), str_1.end());
89                 return sum;
90             }
91         }
92     }
93 };

4. 反思