ONE-WAY

one-way linked list

 struct ELEMENT {
    int               value;
    struct ELEMENT    *next;
};

struct ELEMENT *head;



 * a field named value will serve as storage for any useful values;
 * a field named next will be used to “attach” to the next structure in the chain;
 * the first structure in the chain is “attached” to a head variable, declared as follows:
    - struct ELEMENT *head;

 * the last structure in the chain will be attached to nothing, so we’ll assign the NULL pointer value to its next field.


struct ELEMENT {
 int              value;
 struct ELEMENT  *next;
};

struct ELEMENT *head, *ptr;

/* the one-way linked list is created here
   we don't know yet how it was done
   we only know that the head points to element #1 */
ptr = head;
/* ptr points to the first element now; we will move it
   through all elements until we reach the end */
while(ptr != NULL) { 
    /* print the value stored in the element */
    printf("value = %d\n", ptr -> value);

    /* move ptr to the next element */
    ptr = ptr -> next;
}
printf("done!");

BASIC EXAMPLE: CONSTRUCTION AND USAGE

#include <stdio.h>
#include <stdlib.h>

struct ELEMENT {
    int value;
    struct ELEMENT *next;
};

int main() {
    struct ELEMENT *head = NULL;
    struct ELEMENT *second = NULL;
    struct ELEMENT *third = NULL;

    // Allocate memory
    head = (struct ELEMENT *)malloc(sizeof(struct ELEMENT));
    second = (struct ELEMENT *)malloc(sizeof(struct ELEMENT));
    third = (struct ELEMENT *)malloc(sizeof(struct ELEMENT));

    // Assign values and link elements
    head->value = 10;
    head->next = second;

    second->value = 20;
    second->next = third;

    third->value = 30;
    third->next = NULL;

    // Traverse and print
    struct ELEMENT *ptr = head;
    while (ptr != NULL) {
        printf("value = %d\n", ptr->value);
        ptr = ptr->next;
    }
    printf("done!\n");

    // Cleanup
    free(head);
    free(second);
    free(third);

    return 0;
}

REAL-WORLD EXAMPLE: task manager storing tasks in a to-do list

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define MAX_TASK_NAME 100

struct Task {
    char name[MAX_TASK_NAME];
    struct Task *next;
};

int main() {
    struct Task *head = NULL;
    struct Task *task1 = NULL;
    struct Task *task2 = NULL;

    // Allocate memory
    task1 = (struct Task *)malloc(sizeof(struct Task));
    task2 = (struct Task *)malloc(sizeof(struct Task));

    // Assign data
    strcpy(task1->name, "Submit CNODP Application");
    task1->next = task2;

    strcpy(task2->name, "Study Windows System Programming");
    task2->next = NULL;

    // Set head
    head = task1;

    // Print task list
    struct Task *ptr = head;
    while (ptr != NULL) {
        printf("Task: %s\n", ptr->name);
        ptr = ptr->next;
    }
    printf("All tasks listed.\n");

    // Cleanup
    free(task1);
    free(task2);

    return 0;
}