package Stack;

/**
 * 顺序栈(基于数组实现)
 * Author: PeiJiaNi
 */
public class StackBaseArray {
 private int[] items; // 数组
 private int count; // 栈中元素个数
 private int length; // 栈空间大小

 public StackBaseArray(int capactiy) {
 this.items = new int[capactiy];
 this.count = 0;
 this.length = capactiy;
 }

 /**
 * 入栈操作 时间复杂度O(1)
 * @param item 要入栈的元素
 * @return 入栈成功则返回true,否则返回false
 */
 public boolean push(int item) {
 if(count == length) {
 System.out.println("当前栈已满,无法进行入栈操作");
 return false;
 }
 items[count] = item;
 ++count;
 return true;
 }

 /**
 * 出栈操作 时间复杂度O(1)
 * @return 如果栈内不为空,则返回栈顶元素,否则返回-1
 */
 public int pop(){
 if(count == 0) {
 System.out.println("当前栈已空,无法进行出栈操作");
 return -1;
 }

 // 返回下标为 count-1 的数组元素,并且栈中元素个数count-1
 return items[--count];
 }

 public static void main(String[] args){
 StackBaseArray stack = new StackBaseArray(6);
 stack.push(1);
 stack.push(2);
 stack.push(3);
 stack.push(4);
 stack.push(5);
 System.out.println(stack.pop());
 System.out.println(stack.pop());
 System.out.println(stack.pop());
 System.out.println(stack.pop());
 System.out.println(stack.pop());

 }


}