Sigbrt Error

Why am I getting Sigbrt error for this simple code while in my IDE its working fine…

int size;
cin >> size;
string str;
int zero = 0, one = 0;
for (int i = 0; i < size; i++)
cin >> str[i];
for(int i=0;i<size;i++)
{
if(str[i]==‘0’)
zero++;
else if(str[i]==‘1’)
one++;
}
int mn=min(zero,one);
if(mn==0)
mn++;
ans[v]=mn-1;