299. Bulls and Cows

class Solution {
public:
string getHint(string secret, string guess) {
int len1=secret.size();
int bulls =0,cows=0;
int d[10]={0};
for(int i=0;i<len1;i++)
{
if(secret[i]==guess[i])
{
bulls++;
guess[i]='a';
}
else d[secret[i]-'0']++;

}
for(int i=0;i<len1;i++)
{
if(guess[i]!='a'&&d[guess[i]-'0'])
{
cows++;
d[guess[i]-'0']--;
}
}
string a;
int n1=log(bulls+0.01)/log(10);
int n2=log(cows+0.01)/log(10);
if(bulls==0) a.push_back('0');
for(int m1=pow(10,n1);m1>=1;m1/=10)
{
int i=bulls/m1%10;
a.push_back('0'+i);
}
a.push_back('A');
if(cows==0) a.push_back('0');
for(int m2=pow(10,n2);m2>=1;m2/=10)
{
int i=cows/m2%10;
a.push_back('0'+i);
}
a.push_back('B');
return a;
}
};