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122:
123:
124: // Tail node is just a sentinel
125:
126: class TailNode : public Node
127: {
128: public:
129: TailNode(){}
130: virtual ~TailNode(){}
131: virtual Node * Insert(Data * theData);
132: virtual void Show() const { }
133:
134: private:
135:
136: };
137:
138: // If data comes to me, it must be inserted before me
139: // as I am the tail and NOTHING comes after me
140: Node * TailNode::Insert(Data * theData)
141: {
142: InternalNode * dataNode = new InternalNode(theData, this);
143: return dataNode;
144: }
145:
146: // Head node has no data, it just points
147: // to the very beginning of the list
148: class HeadNode : public Node
149: {
150: public:
151: HeadNode();
152: virtual ~HeadNode() { delete myNext; }
153: virtual Node * Insert(Data * theData);
154: virtual void Show() const { myNext->Show(); }
155: private:
156: Node * myNext;
157: };
158:
159: // As soon as the head is created
160: // it creates the tail
161: HeadNode::HeadNode()
162: {
163: myNext = new TailNode;
164: }
165:
166: // Nothing comes before the head so just
167: // pass the data on to the next node
168: Node * HeadNode::Insert(Data * theData)
169: {
170: myNext = myNext->Insert(theData); |
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continues |
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