LeetCode 实战技巧 2025：Python 编程算法解析与项目案例分享

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

class LRUCache:
    def __init__(self, capacity):
        self.capacity = capacity
        self.cache = {}
        self.head = ListNode()
        self.tail = ListNode()
        self.head.next = self.tail
        self.tail.prev = self.head

    def _remove(self, node):
        node.prev.next = node.next
        node.next.prev = node.prev

    def _add(self, node):
        node.next = self.head.next
        node.prev = self.head
        self.head.next.prev = node
        self.head.next = node

    def get(self, key):
        if key in self.cache:
            node = self.cache[key]
            self._remove(node)
            self._add(node)
            return node.val
        return -

    def put(self, key, value):
        if key in self.cache:
            node = self.cache[key]
            node.val = value
            self._remove(node)
            self._add(node)
        else:
            new_node = ListNode(key, value)
            self.cache[key] = new_node
            self._add(new_node)
            if len(self.cache) > self.capacity:
                removed = self.tail.prev
                self._remove(removed)
                del self.cache[removed.key]

import heapq

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

def mergeKLists(lists):
    heap = []
    for node in lists:
        if node:
            heapq.heappush(heap, (node.val, node))
    dummy = ListNode()
    current = dummy
    while heap:
        val, node = heapq.heappop(heap)
        current.next = node
        current = current.next
        if node.next:
            heapq.heappush(heap, (node.next.val, node.next))
    return dummy.next

import pytest

def test_merge_sorted_arrays():
    nums1 = [,,,,,]
    m = 
    nums2 = [,,]
    n = 
    merge(nums1, m, nums2, n)
    assert nums1 == [,,,,,]

    nums1 = []
    m = 
    nums2 = []
    n = 
    merge(nums1, m, nums2, n)
    assert nums1 == []