160. Intersection of Two Linked Lists

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode *getIntersectionNode(ListNode *headA, ListNode *headB) {
    
    // A = listA + intersection + listB + intersection
    // B = listB + intersection + listBA + intersection
    
       if (headA == NULL || headB == NULL) return NULL;
       ListNode *A = headA, *B = headB;
        while(A!=NULL&&B!=NULL&&A!=B)
        {
            A = A->next;
            B = B->next;
            
            if(A==B) return A;
            
            if(A==NULL) A = headB;
            if(B==NULL) B = headA;
        }
        return A;
    }
};