反转链表

class ListNode:
    def __init__(self, val=0, next=None):
        self.val = val
        self.next = next

def solve():
    def reverseList(head):
        prev = None
        curr = head
        while curr:
            next_temp = curr.next
            curr.next = prev
            prev = curr
            curr = next_temp
        return prev
    head = ListNode(1, ListNode(2, ListNode(3, ListNode(4, ListNode(5)))))
    result = reverseList(head)
    vals = []
    while result:
        vals.append(result.val)
        result = result.next
    print(vals)