67. Add Binary
Given two binary strings, return their sum (also a binary string).
For example,
a = "11"
b = "1"
Return "100"
.
class Solution {
public:
string addBinary(string a, string b)
{
int la = a.size();
int lb = b.size();
if (la == 0)
return b;
else if (lb == 0)
return a;
int k = max(la, lb) + 1;
for (int i = la; i < k; i++)
a = "0" + a;
for (int i = lb; i < k; i++)
b = "0" + b;
int flag = 0;
for(int i = k - 1; i >= 0; i--)
{
if (flag == 0)
{
if(a[i]=='1' && b[i]=='1')
{
a[i] = '0';
flag = 1;
}
else if ((a[i]=='1' && b[i]=='0') || (a[i]=='0' && b[i]=='1'))
a[i] = '1';
}
else
{
if((a[i]=='1' && b[i]=='0') || (a[i]=='0' && b[i]=='1'))
{
a[i] = '0';
}
else if(a[i]=='0' && b[i]=='0')
{
a[i] = '1';
flag = 0;
}
}
}
return (a[0] == '1') ? a : a.substr(1, a.size()-1);
}
};