Intersection of Two Linked Lists

Leetcode 160.

lengthA = Linked List A
lengthB = Linked List B
key point : lengthA + lengthB = lengthB + lengthA
So, Double pointers can be used here.

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/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */
public class Solution {
    public ListNode getIntersectionNode(ListNode headA, ListNode headB) {
        if(headA == null || headB == null) 
          return null;
       ListNode A = headA, B = headB;
       while(A != B){
         A = A == null ? headB : A.next;
         B = B == null ? headA : B.next;
       }
       return A;
    }
}