160. Intersection of Two Linked Lists

class Solution {public:    ListNode *getIntersectionNode(ListNode *headA, ListNode *headB) {        if(0 == headA || headB == 0)            return NULL;        int len1 = 0, len2 = 0;        ListNode *p;        for(p = headA; p != NULL; p = p->next, ++len1);        for(p = headB; p != NULL; p = p->next, ++len2);        ListNode *p1 = headA, *p2 = headB;        if(len1 > len2){            int gap = len1 - len2;            while(gap--){                p1 = p1->next;            }        }else if(len2 > len1){            int gap = len2 - len1;            while(gap--){                p2 = p2->next;            }        }        while(p1 && p2){            if(p1 == p2)                return p1;            p1 = p1->next; p2 = p2->next;        }        return NULL;    }};