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LINKED LISTSMidwestern State UniversityCMPS 1053Dr. Ranette Halverson

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Basic LL Nodestruct Node{ int Num;

Node * Next;}Node *Head, *Temp;

Num Next

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Traverse a Linked List (print)

// Print each value of the listTemp = Head;while (Temp != NULL){ cout << Temp -> Num;

Temp = Temp -> Next;}

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Insert Node to Front of Listif (Head == Null) // empty list{ Head = new Node;

Head -> Num = VAL;Head -> Next = NULL; }

else // not empty list{ Temp = new Node;

Temp -> Num = VAL;Temp -> Next = Head;Head = Temp; }

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Insert Node to Front of List - Revisited

Could we eliminate the first case (Head == NULL)?

That is, does the second case work with an empty or non-empty list?

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Insert Node to Front of Listif (Head == Null) // Can we eliminate this case?{ Head = new Node;

Head -> Num = VAL;Head -> Next = NULL; }

else // Test this for empty list: Head == Null{ Temp = new Node;

Temp -> Num = VAL;Temp -> Next = Head;Head = Temp; }

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Remove Front Node From List

if (Head != NULL){ Temp = Head;

Head = Head -> Next; delete Temp;Temp = NULL;

}

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Insert Node to End of ListNode *P, *C; // for previous & currentif (Head == NULL) { } //Use insert to front code;else {P = Head; C=Head -> Next; While (C != NULL) // find end of list

{ P = C; C = C -> Next; } P -> Next = new Node; P -> Next -> Num = VAL; P -> Next -> Next = Null;}

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Remove Last Node in Listif (Head != NULL) // empty listelse if (Head -> Next == NULL) //one Node in list{ delete Head; Nead = Null; } else // find end of list having at least 2 Nodes{ P = Head; C = Head -> Next; While (C -> Next != NULL) // C will point to last Node

{ P = C; C = C -> Next; } delete C; C = Null; P -> Next = NULL; }

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Insert Node (Val) to Ordered List (ascending)

Temp = new Node; Temp -> Num = Val;//Case 1: Empty list – use code to insert to frontif (Head == NULL) { } //Case 2: Val is smaller than first Node – insert to frontelse if (Val <= Head -> Num) { } //Case 3: Find correct location within the listelse { // need to write this code }//Considerations: Search list comparing Val to Nodes already in list AND watching for end of list (NULL)

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Insert Node in Ordered List (p.2)

//Case 3: Find correct location within the list{ P = NULL; C = Head; while (C -> Next != Null && C-> Num < Val) //move down list { P = C; C = C -> Next;}// found location – don’t know which condition stopped the loop if (C -> Num >= Val) // Insert between P & C { Temp -> Next = C; P -> Next = Temp; } else // Insert after C { C -> Next = Temp; Temp->Next = NULL; }

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Remove Node (Val) from Linked List

if (Head == Null) { return false; } // empty listelse if (Head ->Num == Val) // delete first node { Temp = Head; Head = Head -> Next; delete Temp; Temp = Null; return true; }

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Remove Node (Val) from Linked Listelse // must find val in list { P=Null; C = Head; while (C -> Next != Null && C-> Num < Val) { P = C; C = C -> Next;} if ( C -> Num == Val) // remove node { P -> Next = C -> Next;

delete C; C = Null; return true; } else { return false; } // val not in list }

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Linked List Classstruct Node{ int Num;

Node * Next;}class LinkList{ Node *Head; public: // put functions here}

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Constructor

LinkList ( ){ Head = NULL;}

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Insert to Front Functionvoid InsertFront (int Val){ Node * Temp; if (Head == Null) // empty list { Head = new Node;

Head -> Num = VAL;Head -> Next = NULL; }

else // not empty list { Temp = new Node;

Temp -> Num = VAL;Temp -> Next = Head;Head = Temp; }

}

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Remove From Front of Listbool RemoveFront (int &Val){ if (Head == Null) // Empty list

return false; else if (Head != NULL) { Val = Head -> Num;

Temp = Head;Head = Head -> Next; delete Temp;Temp = NULL;return true;

}}

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Calls to Insert & Removeint main ( ){ LinkList MyList ( );

int X = 5, Y = 10, Z; bool B;MyList.InsertFront(X);MyList.InsertFront(Y);B = MyList.RemoveFront (Z);if (B) cout << Z; // only print if actually removed

MyList.PrintList ( );}

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NOW, YOU DEVELOP YOUR OWN LINKED LIST CLASS USING WHAT WE HAVE DONE IN CLASS!!!

Test with your own data. Test all functions thoroughly!!!

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Linked List Application

Consider a linked list consisting of a person’s last & first names & age, ordered by age.• Modify the struct Node• What function do you call to insert a new person to the list?

• How does the code in other member functions change?

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New structstruct Node{ string Lname;

string Fname;int Age; // NumNode * Next;

}• Does the order of the attributes matter?• If we use Num (instead of Age) will have less code changes.

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Code Changes???

•Every place that Num in a node is assigned, also need to assign last name & first name.

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Constructor – any changes needed?

LinkList ( ){ Head = NULL;}

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Traverse to Print

//Print each value of the listTemp = Head;while (Temp != NULL){ cout << Temp-> Lname << Temp-> Fname <<Temp -> Num << endl;

Temp = Temp -> Next;}

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Insert Ordered – (Val, LN, FN)Temp = new Node; Temp -> Num = Val; Temp -> Lname = LN; Temp -> Fname = FN;if (Head == NULL) { // insert to front code here } else if (Val <= Head -> Num) { // insert to front code here } else{ P = NULL; C = Head; while (C -> Next != Null && C-> Num < Val) //move down list { P = C; C = C -> Next;} if (C -> Num >= Val) //insert between P & C { Temp -> Next = C; P -> Next = Temp; } else // Insert after C { C -> Next = Temp; Temp->Next = NULL }}

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Question?

•What happens if there is a “Tie” in the ages? That is, if 2 people have the same age which one is first in the list?