[leetcode刷题系列]Add Binary

class Solution {
public:
string addBinary(string a, string b) {
// Start typing your C/C++ solution below
// DO NOT write int main() function
reverse(a.begin(), a.end());
reverse(b.begin(), b.end());
string ans = "";
int carry = 0;
int len = max(a.size(), b.size());
for(int i = 0; i < len; ++ i){
int ca = 0;
if(i < a.size())
ca = a[i] - '0';
int cb = 0;
if(i < b.size())
cb = b[i] - '0';
int sum = ca + cb + carry;
carry = sum / 2;
ans += sum % 2 + '0';
}
if(carry)
ans += '1';
reverse(ans.begin(), ans.end());
return ans;
}
};