/**
knakul853
 */
class Solution {
public:
    ListNode *getIntersectionNode(ListNode *headA, ListNode *headB) {

        ListNode* a = headA;
        ListNode* b = headB;
        // let A travels a+c (c is the common distance ) and B travels b+c
        // after assigning the pointers to the other side bothe tarvels a+b+2*c

        while( a!= b )
        {
            a = a == NULL ? headB : a->next;
            b = b == NULL ? headA : b->next;

        }

        return a;



    }
};