ListNode *detectLoop(ListNode *head){

    ListNode *slow=head,*fast=head;
    while(fast != NULL && fast->next != NULL){
        fast=fast->next->next;
        slow=slow->next;

        if(slow==fast)
            return slow;
    }
    return NULL;
}

ListNode* getIntersectionNode(ListNode *A, ListNode *B) {

    //make any one list as circular
    ListNode *p=A;
    while(p->next != NULL)
        p=p->next;

    ListNode *last=p;
    p->next=A;

    //Now A is circular and this problem is converted into
    //find loop in a LL
    ListNode *q=detectLoop(B);
    //p=detectLoop(B);

    if(!q)  {
        last->next=NULL;
        return NULL;
    }

    p=B;
    while(p != q){
        p=p->next;
        q=q->next;
    }

    last->next=NULL;
    return p;
}