【LeetCode】67 - Add Binary

 1 class Solution {
 2 public:
 3     string addBinary(string a, string b) {
 4         int sizea=a.size(),sizeb=b.size();
 5         if(sizea<sizeb)return addBinary(b,a);
 6         int n=sizea-sizeb;
 7         string helper(n,‘0‘);
 8         b = helper + b;
 9         int carry=0;
10         for(int i=sizea-1;i>=0;i--){
11             int sum=(a[i]-‘0‘)+(b[i]-‘0‘)+carry;
12             if(sum==0);
13             else if(sum==1){
14                 a[i]=‘1‘;
15                 carry=0;
16             }else if(sum==2){
17                 a[i]=‘0‘;
18                 carry=1;
19             }else if(sum==3){
20                 a[i]=‘1‘;
21                 carry=1;
22             }
23         }
24         if(carry==1)a=‘1‘+a;
25         return a;
26     }
27 };