From 7e0f021a9aec35fd8e6725e87e3313b101d26f5e Mon Sep 17 00:00:00 2001 From: Tobias Klauser Date: Sun, 27 Jan 2008 11:37:44 +0100 Subject: Initial import (2.0.2-6) --- reference/C/MISC/linklists.html | 119 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 119 insertions(+) create mode 100644 reference/C/MISC/linklists.html (limited to 'reference/C/MISC/linklists.html') diff --git a/reference/C/MISC/linklists.html b/reference/C/MISC/linklists.html new file mode 100644 index 0000000..f17b58d --- /dev/null +++ b/reference/C/MISC/linklists.html @@ -0,0 +1,119 @@ +Link Lists + +
+

Link Lists

+
+

+

+ + +Question, how would you write a program to meet the following requirements? + +
    +
  1. Read an unknown number of records from a file into memory. A typical +record would look like: +
    +	Ref  Title	  Cost
+	---  -----	  ----
+	1234 Oracle_Guide 22.95
+
    +
  2. Perform a numeric sort based on the first field. +
  3. Delete duplicate records based on the first field. +
+ +One method is to define an +array of records as below: + +
+	main()
+ 	{
+	  char array[50][80]; /* 50 records, 80 bytes long	*/
+	}
+
+ +The data can then be read into the array and then actions performed +on the data. +This is OK but has some major problems. +
    +
  1. The arrary will hold all the data in character format. It would be +nice to hold the integer and decimal numbers in a more appropriate form. +
  2. If you have more than 50 records the program has to be altered +and recompiled. +
+The first problem could be fixed by defining an +array of structures BUT both problems +can be solved with linked lists.

+ + + + +

+The concept of a linked list is fairly simple. It is a group of structures +linked together by pointers, here is a picture:

+
+

+

+The "Name Age Pointer" block could be defined as below: +

+	struct record {char name[20]; int age; struct record *next_rec;}; 
+
+ +The important bit is "struct record *next_rec" this is the pointer to the next +structure (record). It will either point to the next record which +will require memory reserved +with the malloc function or +NULL if its the last record. +

+ +

Examples

+ + + Here is the first example. +This program is more complicated than I would +like, but its the simplest I can come up with. +
+

+ + +This is the same program but without the heavy commenting. +
+

+ + +This is still the same program but it is slightly simplified with the use +of typedef. +
+ +

+

+

+ + + + +
+Top + +Master Index + +C Keywords + +Functions +
+
+

+ + + +

+
Martin Leslie + +
+ -- cgit v1.2.3-54-g00ecf e:
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