Question

Here is my code for the problem. The code is running fine on my Code::blocks but not on spoj site and on ideone.com.I get a runtime error. I guess the spoj server cannot allocate the required amount of memory. Please give some suggestions.

http://paste.ubuntu.com/1277109/ ( MY code )

Answer 1

Your code is declaring an empty string s and then is assigning to elements of it…

...
string s,res;int c=0;
int sum,carry=0;
for(int i=m-1;i>=0;i--)
{
    sum=(a[i]-'0')*2+carry;
    s[c]=sum%10+'0';         // This is undefined behavior, s is empty
    carry=sum/10;
    c++;
}
...