一个数组实现两个栈

        基本思路：

                1.定义两个栈顶top1=-1，top2=maxsize

                2.栈满，当top1与top2相差1时栈满

 

package 例题;
//一个数组实现两个栈
public class TwoStack {
    private int[] arr;
    private int maxSize;
    //定义栈顶
    private int top1;
    private int top2;

    public  TwoStack(int maxSize) {
        if (maxSize<2){
            System.out.println("数组大小不能小于2");
            return;
        }
        this.maxSize = maxSize;
        arr=new int[maxSize];
        top1=-1;
        top2=maxSize;
    }
    //入栈
    public void push(int stackid,int value){
        if (top1+1==top2){
            System.out.println("已满");
            return;
        }
        if (stackid==1){
            top1++;
            arr[top1]=value;
        }else if (stackid==2){
            top2--;
            arr[top2]=value;
        }else {
            System.out.println("没有这个栈");
            return;
        }
    }
    //出栈
    public int pop(int stackid) throws Exception{
        if (stackid==1){
            if (top1==-1){
                throw new Exception("栈1为空");
            }
            return arr[top1--];
        }else if (stackid==2){
            if (top2==maxSize){
                throw new Exception("栈2为空");
            }
            return arr[top2++];
        }else {
            throw new Exception("没有这个栈");
        }
    }
    public void list(int stackid){
        if (stackid==1){
            for (int i =0; i <=top1 ; i++) {
                System.out.println("stack["+i+"]="+arr[i]);
            }
        }
        else if (stackid==2){
            for (int i =maxSize-1; i >=top2 ; i--) {
                System.out.println("stack["+i+"]="+arr[i]);
            }
        }else {
            System.out.println("没有这个栈");
        }

    }
}