【LeeCode】栈和队列

​​学习参考​​

【栈】

import java.util.*;
// 2022-12-15

// 栈：先进后出
class MyStack {
public int[] elem;
public int useSize;

public MyStack(){
this.elem = new int[10];
    }

// 是否栈满
public boolean isFull(){
if (this.useSize == this.elem.length){
return true;
        }
return false;
    }

public void push(int item){
if (isFull()){
this.elem = Arrays.copyOf(this.elem, 2*2*this.elem.length);
        }
this.elem[useSize] = item;
this.useSize++;
    }
public boolean empty(){
if (this.useSize == 0) return true;
return false;
    }

// 弹出栈顶的值, 删除元素
public int pop(){
if (empty()){
throw new RuntimeException("栈空了");
        }
int val = this.elem[this.useSize - 1];   // 先进后出   pop输出最后一个
this.useSize--;
return val;
    }

// 弹出栈顶的值， 不删除原来的栈元素
public int peek(){
if (empty()){
throw new RuntimeException("栈空了");
        }
return this.elem[this.useSize - 1];
    }
}

public class Main{
public static void main(String[] args) {
int[] arr = {1, 2, 3, 4, 5, 6};
MyStack myStack = new MyStack();
myStack.elem = arr;
myStack.useSize = 6;
myStack.pop();
    }
}

【队列】