数据结构：

线性结构：

顺序存储方式，顺序表

常见的顺序存储结构有：数组、队列、链表、栈

链式存储方式，链表

 队列：

队列可以使用数组结构或者链表结构来存储，先入先出，后进后出。

数组结构的队列：

public class Demo {public static void main(String[] args) {CircleArrayQueue arrayQueue = new CircleArrayQueue(3);char key;Scanner scanner = new Scanner(System.in);boolean loop = true;while (loop) {System.out.println("s(show)：显示队列");System.out.println("e(exit)：退出程序");System.out.println("a(add)：添加数据到队列");System.out.println("g(get)：从队列取出数据");System.out.println("h(head)：查看队列头的数据");key = scanner.next().charAt(0);switch (key) {case 's':arrayQueue.showQueue();break;case 'a':System.out.println("请输入一个数字");int value = scanner.nextInt();arrayQueue.addQueue(value);break;case 'g':try {int res = arrayQueue.getQueue();System.out.println("取出的数据为=" + res);} catch (Exception e) {System.out.println(e.getMessage());}break;case 'e':loop = false;scanner.close();System.out.println("程序退出...");break;case 'h':try {int res = arrayQueue.headQueue();System.out.println("查看的数据为=" + res);} catch (Exception e) {System.out.println(e.getMessage());}break;default:break;}}}
}class CircleArrayQueue {private int maxSize;// 指向队列头的位置private int front;// 指向队列尾的数据的下一个的位置，它指向的队尾的数据代表有值的private int rear;private int[] arr;public CircleArrayQueue(int arrMaxSize) {// 实际上队列有maxSize个元素，因为空出了一个位置maxSize = arrMaxSize + 1;arr = new int[maxSize];front = rear = 0;}public boolean isFull() {return (rear + 1) % maxSize == front;}public boolean isEmpty() {return front == rear;}public void addQueue(int n) {if (isFull()) {System.out.println("队列为满，不能加入数据");return;}arr[rear] = n;rear++;if (rear % maxSize == 0) {rear = 0;}}public int getQueue() {if (isEmpty()) {throw new RuntimeException("队列为空，不能取值");}int res = arr[front];front++;if (front % maxSize == 0) {front = 0;}return res;}public void showQueue() {if (isEmpty()) {System.out.println("队列为空，没有数据");return;}
//        for (int i = front; i != rear; i = (i + 1) % maxSize) {for (int i = front; i < front + size(); i++) {System.out.printf("arr[%d]=%d\n", i % maxSize, arr[i % maxSize]);}}public int headQueue() {if (isEmpty()) {throw new RuntimeException("队列为空，没有头数据");}return arr[front];}private int size() {return (rear + maxSize - front) % maxSize;}
}

链表结构的队列：

public class SingleLinkListDemo {public static void main(String[] args) {HeroNode hero1 = new HeroNode(1, "宋江", "及时雨");HeroNode hero2 = new HeroNode(2, "卢俊义", "玉麒麟");HeroNode hero3 = new HeroNode(3, "吴用", "智多星");SingleLinkList singleLinkList = new SingleLinkList();singleLinkList.add(hero3);singleLinkList.add(hero2);singleLinkList.add(hero1);
//        singleLinkList.add(hero3);
//        HeroNode newHero = new HeroNode(3, "张三", "法外狂徒");
//        singleLinkList.update(newHero);HeroNode delHero1 = new HeroNode(1, "", "");singleLinkList.del(delHero1);singleLinkList.reverse();singleLinkList.list();}
}class SingleLinkList {private HeroNode headNode = new HeroNode(0, "", "");// 非递归反转public void reverse3() {if (headNode.getNext() == null || headNode.getNext().getNext() == null) {return;}HeroNode nextNode1, nextNode2, nextNode3;nextNode1 = headNode.getNext();nextNode2 = nextNode1.getNext();nextNode3 = nextNode2.getNext();nextNode2.setNext(nextNode1);nextNode1.setNext(null);while (nextNode3 != null) {nextNode1 = nextNode2;nextNode2 = nextNode3;nextNode3 = nextNode3.getNext();nextNode2.setNext(nextNode1);}headNode.setNext(nextNode2);}// 递归反转public void reverse() {HeroNode nextNode = headNode.getNext();headNode.setNext(reverse2(headNode.getNext()));nextNode.setNext(null);}private HeroNode reverse2(HeroNode heroNode) {if (heroNode.getNext() != null) {HeroNode lastNode = reverse2(heroNode.getNext());heroNode.getNext().setNext(heroNode);return lastNode;}return heroNode;}public void del(HeroNode delHeroNode) {if (headNode.getNext() == null) {System.out.println("链表为空");return;}HeroNode preNode, nextNode;preNode = headNode;nextNode = headNode.getNext();while (nextNode != null) {if (nextNode.getNo() == delHeroNode.getNo()) {preNode.setNext(nextNode.getNext());// nextNode.setNext(null);return;}preNode = nextNode;nextNode = nextNode.getNext();}System.out.println("删除编号= " + delHeroNode.getNo() + " 的元素没有找到");}public void update(HeroNode newHeroNode) {if (headNode.getNext() == null) {System.out.println("链表为空");return;}HeroNode preNode, nextNode;preNode = headNode;nextNode = headNode.getNext();while (nextNode != null) {if (nextNode.getNo() == newHeroNode.getNo()) {newHeroNode.setNext(nextNode.getNext());preNode.setNext(newHeroNode);return;}preNode = nextNode;nextNode = nextNode.getNext();}System.out.println("编号= " + newHeroNode.getNo() + " 的元素没有找到");}public void add(HeroNode heroNode) {HeroNode nextNode, preNode;preNode = headNode;nextNode = headNode.getNext();// 头插法if (nextNode == null) {headNode.setNext(heroNode);heroNode.setNext(null);return;}// 中插法while (nextNode != null) {if (heroNode.getNo() < nextNode.getNo()) {preNode.setNext(heroNode);heroNode.setNext(nextNode);return;}// 相同的数据不能进行插入if (heroNode.getNo() == nextNode.getNo()) {System.out.println("编号=" + heroNode.getNo() + " 已存在，不能添加");return;}preNode = nextNode;nextNode = nextNode.getNext();}// 尾插法preNode.setNext(heroNode);heroNode.setNext(null);}public void list() {HeroNode tmpNode = headNode.getNext();if (tmpNode == null) {System.out.println("链表为空");return;}while (tmpNode != null) {System.out.println("node= " + tmpNode + " -->");tmpNode = tmpNode.getNext();}}
}@Data
class HeroNode {private int no;private String name;private String nickName;private HeroNode next;public HeroNode(int hNo, String hName, String hNickName) {this.no = hNo;this.name = hName;this.nickName = hNickName;}@Overridepublic String toString() {return "HeroNode{" +"no=" + no +", name='" + name + '\'' +", nickName='" + nickName + '\'' +'}';}
}

链表的面试题：

单向链表应用场景：

约瑟夫环问题：

代码：

package org.example.josephu;public class Josephu {public static void main(String[] args) {CircleSingleLinkedList list = new CircleSingleLinkedList();list.addBoy(5);list.countBoy(1, 2, 5);
//        list.showBoy();}
}class CircleSingleLinkedList {private Boy first = null;public void addBoy(int nums) {if (nums < 2) {System.out.println("nums的值不正确");return;}Boy curBoy = null;for (int i = 0; i < nums; i++) {Boy boy = new Boy(i + 1);if (i == 0) {first = boy;first.setNext(first);curBoy = first;} else {curBoy.setNext(boy);boy.setNext(first);curBoy = boy;}}}public void showBoy() {if (first == null) {System.out.println("链表为空");return;}Boy curBoy = first;do {System.out.println("编号= " + curBoy.getNo() + " -->");curBoy = curBoy.getNext();} while (curBoy != first);}/*** @param startNo  从第几个开始* @param countNum 数几下* @param nums     最初有多少个小孩*/public void countBoy(int startNo, int countNum, int nums) {if (first == null || startNo < 1 || startNo > nums) {System.out.println("参数输入有误，请重新输入");return;}Boy helper = first;while (helper.getNext() != first) {helper = helper.getNext();}for (int i = 0; i < startNo - 1; i++) {first = first.getNext();helper = helper.getNext();}while (helper != first) {for (int i = 0; i < countNum - 1; i++) {first = first.getNext();helper = helper.getNext();}System.out.println("小孩 " + first.getNo() + " 出圈");first = first.getNext();helper.setNext(first);
//            nums--;}System.out.println("最后留在圈中的小孩编号 " + first.getNo());}
}class Boy {private int no;private Boy next;public Boy(int no) {this.no = no;}//#region get|setpublic int getNo() {return no;}public void setNo(int no) {this.no = no;}public Boy getNext() {return next;}public void setNext(Boy next) {this.next = next;}//#endregion
}

栈结构：

代码：

package org.example.stack;import java.sql.SQLOutput;
import java.util.Scanner;public class ArrayStackDemo {public static void main(String[] args) {ArrayStack stack = new ArrayStack(4);String key;boolean loop = true;Scanner scanner = new Scanner(System.in);while (loop) {System.out.println("show：表示显示栈");System.out.println("exit：表示退出栈");System.out.println("push：表示压栈");System.out.println("pop：表示出栈");System.out.println("请输入你的选择：");key = scanner.next();switch (key) {case "s":stack.list();break;case "e":loop = false;break;case "pu":try {System.out.println("请输入要压栈的数据");int value = scanner.nextInt();stack.push(value);} catch (Exception e) {System.out.println(e.getMessage());}break;case "po":try {System.out.println(stack.pop());} catch (Exception e) {System.out.println(e.getMessage());}break;default:System.out.println("输入有误");break;}}System.out.println("程序退出了...");}
}class ArrayStack {private int maxSize;private int[] stack;private int top = -1;public ArrayStack(int maxSize) {this.maxSize = maxSize;stack = new int[maxSize];}public boolean isFull() {return top == maxSize - 1;}public boolean isEmpty() {return top == -1;}public void push(int value) {if (isFull()) {System.out.println("栈满");return;}top++;stack[top] = value;}public int pop() {if (isEmpty()) {throw new RuntimeException("栈空，没有数据");}int res = stack[top];top--;return res;}public void list() {if (isEmpty()) {System.out.println("栈空，没有数据");return;}for (int i = top; i >= 0; i--) {System.out.printf("a[%d]=%d\n", i, stack[i]);}}
}

用栈实现一个简单的计算器：

中缀表达式：人阅读的表达式。

package org.example.stack;public class Calculator {public static void main(String[] args) {String expression = "7*2*2-5+1-5+3-4";ArrayStack2 numStack = new ArrayStack2(10);ArrayStack2 operStack = new ArrayStack2(10);int index = 0;int num1 = 0;int num2 = 0;int oper = 0;int res = 0;char ch = ' ';while (true) {ch = expression.substring(index, index + 1).charAt(0);if (operStack.isOper(ch)) {if (!operStack.isEmpty()) {if (operStack.priority(ch) <= operStack.priority(operStack.peek())) {num1 = numStack.pop();num2 = numStack.pop();oper = operStack.pop();res = numStack.cal(num1, num2, (char) oper);numStack.push(res);operStack.push(ch);} else {operStack.push(ch);}} else {operStack.push(ch);}} else {// numStack.push(ch - '0');int keepNum = ch - '0';while (index < expression.length() - 1) {index++;ch = expression.substring(index, index + 1).charAt(0);if (!operStack.isOper(ch)) {keepNum = keepNum * 10 + (ch - '0');} else {index--;break;}}numStack.push(keepNum);}index++;if (index == expression.length()) {break;}}while (true) {if (operStack.isEmpty()) {break;}num1 = numStack.pop();num2 = numStack.pop();oper = operStack.pop();res = numStack.cal(num1, num2, (char) oper);numStack.push(res);}System.out.printf("表达式 %s = %d\n", expression, numStack.pop());}
}class ArrayStack2 {private int maxSize;private int[] stack;private int top = -1;public ArrayStack2(int maxSize) {this.maxSize = maxSize;stack = new int[maxSize];}public boolean isFull() {return top == maxSize - 1;}public boolean isEmpty() {return top == -1;}public void push(int value) {if (isFull()) {System.out.println("栈满");return;}top++;stack[top] = value;}public int pop() {if (isEmpty()) {throw new RuntimeException("栈空，没有数据");}int res = stack[top];top--;return res;}public void list() {if (isEmpty()) {System.out.println("栈空，没有数据");return;}for (int i = top; i >= 0; i--) {System.out.printf("a[%d]=%d\n", i, stack[i]);}}public int priority(int oper) {if (oper == '*' || oper == '/') {return 1;} else if (oper == '+' || oper == '-') {return 0;}return -1;}public boolean isOper(char val) {return val == '+' || val == '-' || val == '*' || val == '/';}public int cal(int num1, int num2, char oper) {int res = 0;switch (oper) {case '+':res = num1 + num2;break;case '-':res = num2 - num1;break;case '*':res = num1 * num2;break;case '/':res = num2 / num1;break;default:break;}return res;}public int peek() {return stack[top];}
}

非线性结构：

常见的非线性结构有：二维数组、多维数组、广义表、树结构、图结构