java手动实现常见数据结构的示例代码

int[] array = new int[5]; // 静态数组
array[0] = 10;

import java.util.ArrayList;
ArrayList<Integer> list = new ArrayList<>();
list.add(10);        // 添加元素
int value = list.get(0); // 访问元素

import java.util.LinkedList;
LinkedList<Integer> linkedList = new LinkedList<>();
linkedList.add(10);          // 添加元素
linkedList.addFirst(5);      // 头部插入
int first = linkedList.getFirst(); // 访问头部元素

import java.util.ArrayDeque;
ArrayDeque<Integer> stack = new ArrayDeque<>();
stack.push(10); // 压栈
int top = stack.pop(); // 弹栈

import java.util.Queue;
import java.util.LinkedList;
Queue<Integer> queue = new LinkedList<>();
queue.offer(10); // 入队
int head = queue.poll(); // 出队

import java.util.HashMap;
HashMap<String, Integer> map = new HashMap<>();
map.put("Alice", 25); // 添加键值对
int age = map.get("Alice"); // 查找

import java.util.TreeSet;
TreeSet<Integer> treeSet = new TreeSet<>();
treeSet.add(10);
treeSet.add(5); // 自动排序为 [5, 10]

import java.util.PriorityQueue;
PriorityQueue<Integer> heap = new PriorityQueue<>();
heap.offer(10);
heap.offer(5); // 堆顶为 5
int min = heap.poll(); // 弹出最小值 5

import java.util.*;
class Graph {
    private Map<Integer, List<Integer>> adjacencyList = new HashMap<>();
    public void addEdge(int src, int dest) {
        adjacencyList.computeIfAbsent(src, k -> new ArrayList<>()).add(dest);
        adjacencyList.computeIfAbsent(dest, k -> new ArrayList<>()).add(src); // 无向图
    }
}

import java.util.HashSet;
HashSet<String> set = new HashSet<>();
set.add("Apple");
set.add("Apple"); // 重复元素会被忽略

import java.util.ArrayDeque;
ArrayDeque<Integer> deque = new ArrayDeque<>();
deque.addFirst(10);
deque.addLast(20);
int first = deque.removeFirst();

class Node {
    int data;
    Node next;
    Node(int data) {
        this.data = data;
        this.next = null;
    }
}
class LinkedList {
    Node head;
    public void add(int data) {
        Node newNode = new Node(data);
        if (head == null) {
            head = newNode;
        } else {
            Node current = head;
            while (current.next != null) {
                current = current.next;
            }
            current.next = newNode;
        }
    }
}