import random
N = []

for n in range(10000):
    i = random.randint(1,99999)
    p = random.randint(10000000, 99999999)
    N.append((f"User_{i:05d}", str(p)))

def ll_insert(head, name, phone):
    data = {'name' : name, 'phone' : phone, "next" : None}

    if head is None:
        return data
    
    current = head
    while current:
        if current['name'] == name:
            current['phone'] = phone
            return head
        if current['next'] == None:
            last = current
        current = current['next']
    
    last['next'] = data
    return head


def ll_find(head, name):
    current = head
    while current:
        if current['name'] == name:
            return current['phone']
        current = current['next']
    return None

def ll_delete(head, name):
    if head is None:
        return None
    
    prev = head
    current = head['next']
    while current:
        if current['name'] == name:
            prev['next'] = current['next']
            return head
        prev = current
        current = current['next']
    return head

def ll_list_all(head):
    return None

test_data = None
for name, phone in N:
    test_data = ll_insert(test_data, name, phone)

test_data = ll_insert(test_data, 'User_02000', '99999999')
test_data = ll_insert(test_data, 'User_01000', '99999998')
print(ll_find(test_data, 'User_02000'))
ll_delete(test_data, 'User_02000')
print(ll_find(test_data, 'User_02000'))