C Video Tutorial 10
In this video I continue with my C Linked List tutorial. In part 9, I gave you homework and in this video I will show you my answer. You guys asked for more tutorials like this, so I’m giving it a try.
So, today I’ll show you how to search through a Linked List. I’ll also cover how to delete structs and remove them not only from the Linked List, but also from memory. All of the code from the video is below along with a transcription.
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Code From the Video
CTutorial10.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
struct product {
float price;
char productName[30];
struct product *next;
};
// To traverse the struct linked list I just need to
// track the first and last node in the list
struct product *pFirstNode = NULL;
struct product *pLastNode = NULL;
void createNewList(){
// Set aside enough space in memory for this struct
struct product *pNewStruct = (struct product *) malloc(sizeof(struct product));
// We can assign the value directly for the structs
// reference for the next struct in the linked list
pNewStruct->next = NULL;
printf("Enter Product Name: ");
// The & is needed only because scanf() is used
scanf("%s", &(pNewStruct)->productName);
printf("Enter Product Price: ");
scanf("%f", &(pNewStruct)->price);
// When the first struct is created all of the following
// refer to the same struct
pFirstNode = pLastNode = pNewStruct;
}
void inputData(){
if(pFirstNode == NULL){
createNewList();
} else {
// Set aside enough space in memory for this struct
struct product *pNewStruct = (struct product *) malloc(sizeof(struct product));
printf("Enter Product Name: ");
// The & is needed only because scanf() is used
scanf("%s", &(pNewStruct)->productName);
printf("Enter Product Price: ");
scanf("%f", &(pNewStruct)->price);
// If the first and last struct are equal we know this
// is the second struct in the list
if(pFirstNode == pLastNode){
// Assign the value of next for the first struct to
// this new one since the new one is the second struct
pFirstNode->next = pNewStruct;
// Since this is the second struct we know the last
// struct is equal to this new one
pLastNode = pNewStruct;
// Since this is the last struct in the list it has
// NULL stored in its next
pNewStruct->next = NULL;
} else {
// We know that this is at least the third struct in the
// list so we don't need to touch the pFirstNode.
// We instead just change the pLastNode value for next
// from NULL to our new struct
pLastNode->next = pNewStruct;
pNewStruct->next = NULL;
pLastNode = pNewStruct;
}
}
}
void outputData(){
// This temporarily takes the location of the structs in the
// linked list as we cycle through them to the end
struct product *pProducts = pFirstNode;
printf("Products Entered\n\n");
// Until the ptr reaches a value of NULL for next we'll
// keep printing out values
while(pProducts != NULL){
printf("%s costs %.2f\n\n", pProducts->productName, pProducts->price);
// Switch to the next struct in the list
pProducts = pProducts->next;
}
}
// PART 2 ---------------------------
// NEW : Added For removeProduct
struct product *pProductBeforeProductToDelete = NULL;
// Searches for a struct of a given name and returns it if found
struct product* searchForProduct(char * productName){
// Will hold the current struct as we cycle through them
struct product *pProductIterator = pFirstNode;
// Cycle through the structs in the list until next returns
// NULL which means we reached the end of the list
while(pProductIterator != NULL){
// Compare the first 30 characters of the 2 product names
int areTheyEqual = strncmp(pProductIterator->productName,
productName, 30);
// If strings are equal areTheyEqual will have a value
// of 0, so not is used to make 0 into 1 in that situation
if(!areTheyEqual){
printf("%s was found and it costs %.2f\n\n",
pProductIterator->productName,
pProductIterator->price);
// Return the product struct if found
return pProductIterator;
}
// NEW : Added For removeProduct
pProductBeforeProductToDelete = pProductIterator;
// Cycle to the next product struct in the list
pProductIterator = pProductIterator->next;
}
printf("%s wasn't found\n\n", productName);
return NULL;
}
// PART 3 ---------------------------
void removeProduct(char * productName){
struct product *pProductToDelete = NULL;
pProductToDelete = searchForProduct(productName);
if(pProductToDelete != NULL){
printf("%s Was Deleted\n\n", productName);
// If we want to delete the first product we
// must assign the next product in the list
// to the firstNode
if(pProductToDelete == pFirstNode){
pFirstNode = pProductToDelete->next;
} else {
// Get the product to delete and assign its next
// to the product before the product that is deleted
pProductBeforeProductToDelete->next = pProductToDelete->next;
}
free(pProductToDelete);
} else {
printf("%s Was Not Found\n\n", productName);
}
}
int main(){
inputData();
inputData();
outputData();
// PART 2
searchForProduct("Tomato");
// PART 3
removeProduct("Egg");
removeProduct("Tomato");
outputData();
/*
free(pFirstNode);
free(pLastNode);
*/
}
Hi, I hope you could help me
Do we have free up memory after we finished using the variables
? If not, why?
244 free(pFirstNode);
245
246 free(pLastNode);
If you aren’t using many of them it doesn’t really matter, but it is a good habit to develop
I hope you don’t mine asking you this….
Where do I start if I wanted to teach a computer programming n
Sorry there is a typo error in mine- mind
To continue…… What programming language to teach a 14 years old boy or where do I start to teach computer programming . Thanks for your help and you’re so great and awesome?
The best language for a new programmer in my opinion is Python. I have a Python tutorial if you’re interested.
I’m not sure what you mean by starting to teach a programming language? I’m always happy to help with anything if I can.
derek please start a course of J2EE, u promised me that you will start it soon
I’m going to cover J2EE as soon as I finish my C Tutorial
You’re making it pretty clear and understandable. I am loving it. Will ask you doubts as and when it arises. Thank you !
Thank you 🙂 Feel free to ask questions