Java ACM 模式常用模版

导包

import java.io.*;
import java.util.*;

输入输出

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        int n = sc.nextInt();

        int[] arr1 = new int[n];
        for(int i = 0; i < n; i ++) {
            arr1[i] = sc.nextInt();
        }

        // 读取一行数据，按照空格分割成整数数组
        String[] nums = sc.nextLine().split(" ");
        int[] arr2 = new int[nums.length];
        for(int i = 0; i < nums.length; i ++) {
            arr2[i] = Integer.parseInt(nums[i]);
        }

        // 调用解决方案
        int result = solution(arr1);

        // 输出结果
        System.out.println(result);
    }

    public static int solution(int[] nums) {
        // Todo
        return 0;
    }
}

链表节点定义

// 单向链表
class ListNode {
    int val;
    ListNode next;

    ListNode(){}
    ListNode(int val) {
        this.val = val
    }
    ListNode(int val, ListNode node) {
        this.val = val; 
        this.next = node;
    }
}

// 双向链表
class DoubleListNode {
    int val;
    ListNode pre;
    ListNode next;

    DoubleListNode(){}
    DoubleListNode(int val) {
        this.val = val;
    }
    DoubleListNode(int val, DoubleListNode pre, DoubleListNode next) {
        this.val = val;
        this.pre = pre;
        this.next = next;
    }
}

创建链表

public static ListNode createLinkedList(int[] arr) {
    if (arr == null || arr.length == 0) {
        return null;
    }
    ListNode head = new ListNode(arr[0]);
    ListNode current = head;
    for (int i = 1; i < arr.length; i++) {
        current.next = new ListNode(arr[i]);
        current = current.next;
    }
    return head;
}

二叉树节点定义

class TreeNode {
    int val;
    TreeNode left;
    TreeNode right;

    TreeNode() {}
    TreeNode(int val) {
        this.val = val;
    }

    TreeNode(int val, TreeNode left, TreeNode right) {
        this.val = val;
        this.left = left;
        this.right = right;
    }
}

创建二叉树，根据层序遍历建树

public static TreeNode createTree(Integer[] arr) {
    if(arr == null || arr.length == 0) {
        return null;
    }
    TreeNode root = new TreeNode(arr[0]);
    Queue<TreeNode> queue = new LinkedList<>();
    queue.add(root);

    int i = 1;
    while(i < arr.length) {
        TreeNode cur = queue.poll();
        // 添加左子树
        if(i < arr.length && arr[i] != null) {
            cur.left = new TreeNode(arr[i]);
            queue.add(cur.left);
        }
        i ++;
        // 添加右子树
        if(i < arr.length && arr[i] != null) {
            cur.right = new TreeNode(arr[i]);
            queue.add(cur.right);
        }
        i ++;
    }
    return root;
}