func getInterSectNode(head1, head2 *Node) *Node {
    if head1 == nil || head2 == nil {
        return nil
    }
    loop1 := getLoopNode(head1)
    loop2 := getLoopNode(head2)
    if loop1 == nil && loop2 == nil {
        return noLoop(head1, head2)
    }
    if loop1 != nil && loop2 != nil {
        return bothLoop(head1, loop1, head2, loop2)
    }
    return nil
}

func getLoopNode(head *Node) *Node {
    if head == nil || head.next == nil || head.next.next == nil {
        return nil
    }
    n1 := head.next
    n2 := head.next.next
    for n1 != n2 {
        if n2.next == nil || n2.next.next == nil {
            return nil
        }
        n2 = n2.next.next
        n1 = n1.next
    }
    n2 = head
    for n1 != n2 {
        n1 = n1.next
        n2 = n2.next
    }
    return n1
}

func noLoop(head1, head2 *Node) *Node {
    if head1 == nil || head2 == nil {
        return nil
    }
    cur1 := head1
    cur2 := head2
    n := 0
    for cur1.next != nil {
        n++
        cur1 = cur1.next
    }
    for cur2.next != nil {
        n--
        cur2 = cur2.next
    }
    if cur1 != cur2 {
        return nil
    }
    if n < 0 {
        cur1 = head2
        cur2 = head1
    }
    n = int(math.Abs(float64(n)))
    for n != 0 {
        n--
        cur1 = cur1.next
    }
    for cur1 != cur2 {
        cur1 = cur1.next
        cur2 = cur2.next
    }
    return cur1
}

func bothLoop(head1, loop1, head2, loop2 *Node) *Node {
    var cur1 *Node
    var cur2 *Node
    if loop1 == loop2 {
        cur1 = head1
        cur2 = head2
        n := 0
        for cur1 != loop1 {
            n++
            cur1 = cur1.next
        }
        for cur2 != loop2 {
            n--
            cur2 = cur2.next
        }
        if n < 0 {
            cur1 = head2
            cur2 = head1
        }
        n = int(math.Abs(float64(n)))
        for n != 0 {
            n--
            cur1 = cur1.next
        }
        for cur1 != cur2 {
            cur1 = cur1.next
            cur2 = cur2.next
        }
        return cur1
    } else {
        cur1 = loop1.next
        for cur1 != loop1 {
            if cur1 == loop2 {
                return loop1
            }
            cur1 = cur1.next
        }
        return nil
    }
}