here is a question from codechef...

and here is my code ....

int main()
{
    int t;
    si(t);
    while(t--)
    {
        string A,B;
        cin.ignore();
        getline(cin,A);
        cin>>B;
        for(int i=0;i<A.size();i++)
        {
          if(A[i]==' ')
          continue;
          A[i]= B[(A[i]-'A')];
        }
        cout<<A<<"\n";
    }
    return 0;
}

why am i getting wrong answer afterall i am getting everything correct on my local compiler....

suppose we are given N numbers a1,a2,a3....aN. Now how to write a program which calculates the Lcm of these numbers.....

suppose we want to find a number that starts with N and is divisible by 2520. I found this statement written 'note that there is such number somewhere between N0000 and N2519, inclusive'. Now my question is HOW???????

Can anyone give me some suggestions on how to improving my dynamic programming skills... any link, any pdf, anything.... i am having a lot of trouble ..... Please help me..

suppose we are given a number 'N' and we want to count all integers >=1 and <=N that are divisible by 'A' or 'B' or 'C' and 'D' or 'E' or 'F' then the code for this would be:

int ans=0;
for(int i=1;i<=N;i++)
  if((i%A==0 || i%B==0 || i%C==0) && (i%D==0 || i%E==0 || i%F==0))
      ans++;

cout<<ans;

the above code would run in O(N) time; but suppose 'N' is too big then is there any faster way to accomplish the above task?????

suppose for any 'n' taken as input we want to output (2n)!/n!(n+1)! modulo 1000000007 then which is the fastest way to accomplish this task......

below is the function for adding some number to the end of the linked list.......

int add_at_end(struct node **q,int num)
{
  struct node *temp;
  if(*q==NULL)
  {
    temp= malloc(sizeof(struct node));
    temp->data=num;
    temp->link=NULL;
    *q=temp;
  }
  else
    {
      temp=*q;
      while(temp->link!=NULL)
	{
	  temp=temp->link;
	}
      r=malloc(sizeof(struct node));
      r->data=num;
      r->link=NULL;
      temp->link=r;
    }
  return 0;
}

now my question is what is the need of using double pointer for 'q' , why cant we do the same task using single pointer as below....

int add_at_end(struct node *q,int num)
{
  struct node *temp;
  if(q==NULL)
  {
    temp= malloc(sizeof(struct node));
    temp->data=num;
    temp->link=NULL;
    q=temp;
  }
  else
    {
      temp=q;
      while(temp->link!=NULL)
	{
	  temp=temp->link;
	}
      r=malloc(sizeof(struct node));
      r->data=num;
      r->link=NULL;
      temp->link=r;
    }
  return 0;
}

suppose a class is as follows.. class cool { public: int a; int b; }; cool A[100];

now each element of array A[] has two sub elements 'a' and 'b'. Suppose we want to sort the array A[] in increasing order of 'a' and if two elements have equal 'a' then element with greater 'b' should be before. Can anyone give me the c++ code for the above purpose....