LeetCode Intersection of Two Linked Lists

lenA - lenB

/**
 * 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) {
        if(headA == NULL || headB == NULL) return NULL;
        int lenA = 0, lenB = 0;
        ListNode *p1 = headA, *p2 = headB;
        while(p1 != NULL) {
            lenA++;
            p1 = p1->next;
        }
        while(p2 != NULL) {
            lenB++;
            p2 = p2->next;
        }
        int dis = 0;
        p1 = headA, p2 = headB;
        if(lenA >= lenB) {
            dis = lenA - lenB;
            while(dis != 0) {
                p1 = p1->next;
                dis--;
            }
        }else {
            dis = lenB - lenA;
            while(dis != 0) {
                p2 = p2->next;
                dis--;
            }
        }
        while(p1 != NULL && p2 != NULL) {
            if(p1 == p2) {
                return p1;
            }else {
                p1 = p1->next;
                p2 = p2->next;
            }
        }
        return NULL;
    }
};