Joey LIU | NANTSOU


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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) {
        ListNode a = headA, b = headB;
        int cnta = 0, cntb = 0;

        while (a != null && b != null) {
            a = a.next;
            b = b.next;
        }
        
        while (a != null || b != null) {
            if (a != null) {
                a = a.next;
                cnta++;
            }
            if (b != null) {
                b = b.next;
                cntb++;
            }
        }
        
        while (cnta > 0 || cntb > 0) {
            if (cnta > 0) {
                headA = headA.next;
                cnta--;
            }
            if (cntb > 0) {
                headB = headB.next;
                cntb--;
            }
        }
        
        while (headA != headB) {
            headA = headA.next;
            headB = headB.next;
        }
        
        return headA;
    }
}