From 77eb46e5ffe8ed45510095ff1dcdca1430d26726 Mon Sep 17 00:00:00 2001
From: Christopher Bohn <bohn@unl.edu>
Date: Wed, 26 Jun 2019 22:37:13 -0500
Subject: [PATCH] Robust backing structure, robust size() & push()
---
src/main/java/MyStack.java | 24 ++++++++++++++++++++----
1 file changed, 20 insertions(+), 4 deletions(-)
diff --git a/src/main/java/MyStack.java b/src/main/java/MyStack.java
index c237f86..d1a485d 100644
--- a/src/main/java/MyStack.java
+++ b/src/main/java/MyStack.java
@@ -1,17 +1,33 @@
public class MyStack {
- private Object element;
+ private Node top;
public MyStack() {
super();
- element = null;
+ top = new Node(null, null);
}
public int size() {
- return (element == null) ? 0 : 1;
+ return top.getHeight();
}
public void push(Object element) {
- this.element = element;
+ this.top = new Node(element, top);
+ }
+
+ private class Node {
+ private Object payload;
+ private int height;
+ private Node previous;
+
+ Node(Object payload, Node oldTop) {
+ this.payload = payload;
+ this.previous = oldTop;
+ height = (oldTop == null) ? 0 : oldTop.height+1;
+ }
+
+ Object getPayload() {return payload;}
+ int getHeight() {return height;}
+ Node getPrevious() {return previous;}
}
}
--
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