python 2小时学会八股文-数据结构

1. 数组

# Python 中的数组通常使用列表来实现
arr = [1, 2, 3, 4, 5]  # 创建一个数组
print(arr[0])  # 访问第一个元素

2. 链表

class Node:
    def __init__(self, data):
        self.data = data
        self.next = None

class LinkedList:
    def __init__(self):
        self.head = None

    def append(self, data):
        if not self.head:
            self.head = Node(data)
        else:
            current = self.head
            while current.next:
                current = current.next
            current.next = Node(data)

# 创建链表并添加元素
ll = LinkedList()
ll.append(1)
ll.append(2)

3. 栈

class Stack:
    def __init__(self):
        self.items = []

    def push(self, item):
        self.items.append(item)

    def pop(self):
        return self.items.pop()

    def peek(self):
        return self.items[-1]

    def is_empty(self):
        return len(self.items) == 0

# 使用栈
stack = Stack()
stack.push(1)
stack.push(2)
print(stack.pop())  # 输出 2

4. 队列和双端队列

from collections import deque

# 队列
queue = deque()
queue.append(1)
queue.append(2)
print(queue.popleft())  # 输出 1

# 双端队列
deque = deque()
deque.append(1)
deque.append(2)
deque.appendleft(0)
print(deque.pop())  # 输出 2
print(deque.popleft())  # 输出 0

5. 哈希表

# Python 的字典就是哈希表的实现
hash_table = {}
hash_table['key1'] = 'value1'
print(hash_table['key1'])  # 输出 'value1'

6. 二叉树

class TreeNode:
    def __init__(self, data):
        self.data = data
        self.left = None
        self.right = None

# 创建二叉树
root = TreeNode(1)
root.left = TreeNode(2)
root.right = TreeNode(3)

7. 二叉搜索树

class BSTNode(TreeNode):
    def __init__(self, data):
        super().__init__(data)

class BinarySearchTree:
    def __init__(self):
        self.root = None

    def insert(self, data):
        if not self.root:
            self.root = BSTNode(data)
        else:
            self._insert(self.root, data)

    def _insert(self, node, data):
        if data < node.data:
            if node.left:
                self._insert(node.left, data)
            else:
                node.left = BSTNode(data)
        else:
            if node.right:
                self._insert(node.right, data)
            else:
                node.right = BSTNode(data)

# 使用二叉搜索树
bst = BinarySearchTree()
bst.insert(5)
bst.insert(3)
bst.insert(7)

8. 平衡二叉树 (AVL 树)

class AVLNode(TreeNode):
    def __init__(self, data):
        super().__init__(data)
        self.height = 1

class AVLTree:
    def __init__(self):
        self.root = None

    def insert(self, data):
        self.root = self._insert(self.root, data)

    def _insert(self, node, data):
        # 插入操作
        # 更新高度
        # 检查平衡并调整
        pass

# 使用 AVL 树
avl = AVLTree()
avl.insert(10)
avl.insert(20)
avl.insert(30)

9. 优先队列

import heapq

# 使用列表实现优先队列
priority_queue = []
heapq.heappush(priority_queue, (1, 'low'))
heapq.heappush(priority_queue, (5, 'high'))
print(heapq.heappop(priority_queue))  # 输出 (5, 'high')

10. 并查集

class UnionFind:
    def __init__(self, size):
        self.parent = [i for i in range(size)]
        self.rank = [1] * size

    def find(self, x):
        if self.parent[x] != x:
            self.parent[x] = self.find(self.parent[x])
        return self.parent[x]

    def union(self, x, y):
        rootX = self.find(x)
        rootY = self.find(y)
        if rootX != rootY:
            if self.rank[rootX] > self.rank[rootY]:
                self.parent[rootY] = rootX
            elif self.rank[rootX] < self.rank[rootY]:
                self.parent[rootX] = rootY
            else:
                self.parent[rootY] = rootX
                self.rank[rootX] += 1

# 使用并查集
uf = UnionFind(5)
uf.union(0, 1)
uf.union(1, 2)
print(uf.find(0) == uf.find(2))  # 输出 True

11. 前缀和与差分

def prefix_sum(arr):
    for i in range(1, len(arr)):
        arr[i] += arr[i - 1]
    return arr

def difference_array(arr):
    diff = [0] * len(arr)
    for i in range(1, len(arr)):
        diff[i] = arr[i] - arr[i - 1]
    return diff

# 使用前缀和与差分
arr = [1, 2, 4, 7, 0]
prefix_sum(arr)
difference_array(arr)

12. 线段树

class SegmentTree:
    def __init__(self, data):
        self._build(data, 0, len(data) - 1)

    def _build(self, data, start, end):
        if start == end:
            self.data[start] = data[start]
        else:
            mid = (start + end) // 2
            self._build(data, start, mid)
            self._build(data, mid + 1, end)
            self.data[start] = min(self.data[start], self.data[mid + 1])

    def query(self, start, end):
        # 查询操作
        pass

# 使用线段树
st = SegmentTree([1, 3, 5, 7, 9, 2])

13. 树状数组

def build_tree(arr):
    n = len(arr)
    tree = [0] * (n + 1)
    for i in range(1, n + 1):
        tree[i] = arr[i - 1]
        while i + (i & -i) <= n:
            tree[i + (i & -i)] += tree[i]
    return tree

def query(tree, start, end):
    res = 0
    while start:
        res += tree[start]
        start -= start & -start
    while end:
        res -= tree[end]
        end -= end & -end
    return res

# 使用树状数组
arr = [1, 2, 3, 4, 5]
tree = build_tree(arr)
print(query(tree, 1, 3))  # 输出 6

14. 字典树和后缀数组

class TrieNode:
    def __init__(self):
        self.children = {}
        self.is_end_of_word = False

class Trie:
    def __init__(self):
        self.root = TrieNode()

    def insert(self, word):
        node = self.root
        for char in word:
            if char not in node.children:
                node.children[char] = TrieNode()
            node = node.children[char]
        node.is_end_of_word = True

# 使用字典树
trie = Trie()
trie.insert("hello")
trie.insert("world")