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Linked Lists
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Overview Operations for Lists. Implementation of Linked Lists.
Double Linked Lists.
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List Operations Go to a position in the list.
Insert an item at a position in the list. Delete an item from a position in the list. Retrieve an item from a position. Replace an item at a position. Traverse a list.
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Comparsion Linked Storage Contiguous Storage Unknown list size.
Flexibility is needed. Contiguous Storage Known list size. Few insertions and deletions are made within the list. Random access
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Linked List Head 1 2 3
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#ifndef LINKEDLISTH #define LINKEDLISTH #include <stdbool.h> #include "node.h" struct LinkedListRec { int count; Node* headPtr; }; typedef struct LinkedListRec List; void intializeList(List* listPtr); bool listEmpty(const List* listPtr); Node* setPosition(const List* listPtr, int position); void insertItem(List* listPtr, float item, int position); float deleteNode(List* listPtr, int position); #endif
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Initialize List listPtr addr of list count headPtr NULL
headPtr NULL void initializeList(List* listPtr) { listPtr->headPtr = NULL; listPtr->count = 0; }
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Set Position check if position is within range
start with address of head node set count to 0 while count is less than position follow link to next node increment count return address of current node
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Node* setPosition(const List* listPtr, int position)
{ int i; Node* nodePtr = listPtr->headPtr; if (position < 0 || position >= listPtr->count) { fprintf(stderr, “Invalid position\n”); exit(1); } else { for (i = 0; i < position; i++) { nodePtr = nodePtr->nextPtr; return nodePtr;
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Set Position Head 1 2 2 position
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Set Position Head 0x4000 0x2030 0x30a8 2 position i 0x4000 nodePtr
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Set Position Head 0x4000 0x2030 0x30a8 2 position 1 i 0x2030 nodePtr
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Set Position Head 0x4000 0x2030 0x30a8 2 position 2 i 0x30a8 nodePtr
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Insert Head 1 2 If we insert it at position 0. 1 2 Head
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Insert Head 1 2 If we insert it at position 0. 2 1 3 Head
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Instead, suppose we insert it at position 1.
Head 1 2
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Instead, suppose we insert it at position 1.
Head 3 2 1
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void insertItem(List* listPtr, float item, int position)
{ Node* newNodePtr = makeNode(item); Node* nodePtr = NULL; if (position == 0) newNodePtr->nextPtr = listPtr->headPtr; listPtr->headPtr = newNodePtr; } else nodePtr = setPosition(listPtr, position-1); newNodePtr->nextPtr = nodePtr->nextPtr; nodePtr->nextPtr = newNodePtr; listPtr->count++;
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Inserting – New List Head NULL 0x30a8 position 0x30a8 newNodePtr
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Inserting – New List Head 0x30a8 position 0x30a8 newNodePtr
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Inserting – Start of List
Head Head 0x30a8 0x2008 0x2000 newNodePtr 0x2000 position
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Inserting – Start of List
Head Head 0x30a8 0x2008 0x2000 newNodePtr 0x2000 position
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Inserting – Start of List
Head Head 0x30a8 0x2008 0x2000 newNodePtr 0x2000 position
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Inserting – Inside the List
Head 0x3080 0x3050 nodePtr 0x3080 0x2000 newNodePtr 0x2000 1 position
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Inserting – Inside the List
Head 0x3080 0x3050 nodePtr 0x3080 0x2000 newNodePtr 0x2000 1 position
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Inserting – Inside the List
Head 0x3080 0x3050 nodePtr 0x3080 0x2000 newNodePtr 0x2000 1 position
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Delete Head 1 2 3 If we delete the Node at position 0. 2 1 Head
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If we delete the Node at position 2.
Head 1 2 3
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If we delete the Node at position 2.
Head 2 1 2
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void deleteNode(List* listPtr, int position)
{ Node* oldNodePtr = NULL; Node* nodePtr = NULL; if (listPtr->count > 0 && position < listPtr->count) if (position == 0) { oldNodePtr = listPtr->headPtr; listPtr->headPtr = oldNodePtr->nextPtr; } else { nodePtr = setPosition(listPtr, position - 1); oldNodePtr = nodePtr->nextPtr; nodePtr->nextPtr = oldNodePtr->nextPtr; listPtr->count--; free(oldNodePtr); fprintf(stderr, “List is empty or invalid position.\n”); exit(1);
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Deleting – 1st Node Head 0x4000 0x2030 0x30a8 position 0x4000 nodePtr
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Deleting – 1st Node 0x4000 0x2030 0x30a8 position Head 0x4000 nodePtr
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Deleting – 1st Node 0x2030 0x30a8 position Head 0x4000 nodePtr
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Deleting – Middle Node Head 0x4000 0x2030 0x30a8 1 position 0x2030
nodePtr 0x2030 OldNodePtr
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Deleting – Middle Node Head 0x4000 0x2030 0x30a8 1 position 0x2030
nodePtr 0x2030 OldNodePtr
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Deleting – Middle Node Head 0x4000 0x30a8 1 position 0x2030 nodePtr
OldNodePtr
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Double Linked List Operations
Go to a position in the list. Insert an item in a position in the list. Delete an item from a position in the list. Retrieve an item from a position. Replace an item at a position. Traverse a list, in both directions.
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Double Linked List 1 2 3 4 Current
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struct DoubleLinkNodeRec
{ float value; struct DoubleLinkNodeRec* nextPtr; struct DoubleLinkNodeRec* previousPtr; }; typedef struct DoubleLinkNodeRec Node; struct DoubleLinkListRec int count; Node* currentPtr; int position; typedef struct DoubleLinkListRec DoubleLinkList;
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Insert at end currentPtr prevPtr newPtr 0x4000 0x3080 0x2030 0x2000
NULL NULL NULL 0x4000 0x3080 NULL 0x2030 currentPtr prevPtr newPtr 0x2000
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Insert at end currentPtr prevPtr newPtr 0x4000 0x3080 0x2030 0x2000
NULL NULL 0x4000 0x3080 NULL 0x2030 currentPtr prevPtr newPtr 0x2000
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Insert at end currentPtr prevPtr newPtr 0x4000 0x3080 0x2030 0x2000
NULL NULL 0x4000 0x3080 0x2030 0x2030 currentPtr prevPtr newPtr 0x2000
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Insert inside the list currentPtr prevPtr newPtr 0x4000 0x3080 0x2030
NULL NULL 0x4000 0x3080 0x2000 0x3080 currentPtr prevPtr 0x2000 NULL newPtr NULL
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Insert inside the list currentPtr prevPtr newPtr 0x4000 0x3080 0x2030
NULL NULL 0x4000 0x3080 0x2000 0x3080 currentPtr prevPtr 0x2000 2030 newPtr NULL
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Insert inside the list currentPtr prevPtr newPtr 0x4000 0x3080 0x2030
NULL NULL 0x4000 0x3080 0x2000 0x3080 currentPtr prevPtr 0x2000 2030 newPtr 3080
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Insert inside the list currentPtr prevPtr newPtr 0x4000 0x3080 0x2030
NULL NULL 0x4000 0x2000 0x2000 0x3080 currentPtr prevPtr 0x2000 2030 newPtr 3080
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Insert inside the list currentPtr prevPtr newPtr 0x4000 0x3080 0x2030
NULL NULL 0x4000 0x2000 0x2000 0x3080 currentPtr prevPtr 0x2000 2030 newPtr 3080
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Delete from end currentPtr oldPtr prevPtr 0x4000 0x3080 0x2030 0x3080
NULL NULL 0x4000 0x3080 oldPtr 0x2030 currentPtr 0x3080 prevPtr
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Delete from end currentPtr oldPtr prevPtr 0x4000 0x3080 0x2030 0x3080
NULL NULL NULL 0x4000 0x3080 oldPtr 0x2030 currentPtr 0x3080 prevPtr
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Delete from end currentPtr oldPtr prevPtr 0x4000 0x3080 0x3080 NULL
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Delete from inside list
0x4000 0x3080 0x2030 0x3080 0x2030 NULL NULL 0x4000 0x3080 oldPtr 0x3080 currentPtr 0x4000 prevPtr
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Delete from inside list
0x4000 0x3080 0x2030 0x2030 0x2030 NULL NULL 0x4000 0x3080 oldPtr 0x3080 currentPtr 0x4000 prevPtr
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Delete from inside list
0x4000 0x3080 0x2030 0x2030 0x2030 NULL NULL 0x4000 0x4000 oldPtr 0x3080 currentPtr 0x4000 prevPtr
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Delete from inside list
0x4000 0x2030 0x2030 NULL NULL 0x4000 oldPtr 0x3080 currentPtr Head 0x4000 prevPtr
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Elementary Algorithms
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