public class Solution {
    public ListNode getIntersectionNode(ListNode headA, ListNode headB) {
        if(headA == null || headB == null) return null;
        int depthA = depth(headA);
        int depthB = depth(headB);
        ListNode pA = headA;
        ListNode pB = headB;
        if(depthA >= depthB){
            while(depthA > depthB){
                pA = pA.next;
                depthA--;
            }                
        }else{
            while(depthB > depthA){
                pB = pB.next;
                depthB--;
            }                
        }
        while(pA != null && pB != null){
            if(pA==pB) break;
            pA = pA.next;
            pB = pB.next;
        }
        return pA;
    }
    private int depth(ListNode head){
        int dep = 0;
        ListNode cur = head;
        while(cur != null){
            dep++;
            cur = cur.next;
        }
        return dep;
    }
}