LeetCode - Intersection of Two Linked Lists

Intersection of Two Linked Lists

//
public ListNode getIntersectionNode(ListNode headA, ListNode headB) {
        if(headA == null || headB == null) return null;
        ListNode h1 = headA, h2 = headB;
        while(headA != null && headB != null){
            if(headA == headB) return headA;
            headA = headA.next;
            headB = headB.next;
            if(headA == null && headB == null) return null;
            if(headA == null) headA = h2;
            if(headB == null) headB = h1;
        }
        return null;
    }
//
public ListNode getIntersectionNode(ListNode headA, ListNode headB) {
        if(headA == null || headB == null) return null;
        ListNode p = headA, q = headB;
        boolean flag1 = false, flag2 = false;
        while(p != null && q != null){
            if(p == q) return p;
            p = p.next;
            q = q.next;
            if(p == null){
                if(flag1) break;
                p = headB;
                flag1 = true;
            } 
            if(q == null){
                if(flag2) break;
                q = headA;
                flag2 = true;
            }
        }
        return null;
    }
//
public ListNode getIntersectionNode(ListNode headA, ListNode headB) {
        if(headA==null || headB==null) return null;
        ListNode pA = headA, pB=headB, tailA = null, tailB=null;
        while(true){
            if(pA==null)
                pA = headB;
            if(pB==null)
                pB = headA;
            if(pA.next==null)
                tailA = pA;
            if(pB.next==null)
                tailB = pB;
            if(tailA!=null&&tailB!=null&tailA!=tailB)
                return null;
            if(pA==pB)
                return pA;
            pA = pA.next;
            pB = pB.next;
        }
    }