Linked List

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

typedef struct Person Person;
typedef struct BankLine BankLine;

// struct to represent person
struct Person {
  char name[100];
  int age;
  Person *next;
};

// struct to represent bank line
struct BankLine {
  char name[50];
  Person *head;
  Person *tail;
};

// function to create new bank line in memory
BankLine create_bank_line(char *name) {
  BankLine new_line;
  strcpy(new_line.name, name);
  new_line.head = NULL;
  new_line.tail = NULL;
  return new_line;
}

// function to add a new person to add to the bank line
Person *create_person(char *name, int age) {
  // allocate memory for Person struct
  Person *new_person = malloc(sizeof(Person));
  // set person name
  strcpy(new_person->name, name);
  // set person age
  new_person->age = age;
  // initialize the reference to the next person as NULL
  new_person->next = NULL;
  // tell user about this change
  printf("😁 Someone appeared: %s (%d years old)\n", new_person->name,
         new_person->age);
  // return reference to new person
  return new_person;
}

void add_person_to_line(char *name, int age, BankLine *bank_line) {
  // get reference to new person
  Person *new_person = create_person(name, age);
  // if line has no person, set the head as the new person
  if (bank_line->head == NULL) {
    bank_line->head = new_person;
    printf("  👆 %s is the first person in the line\n", new_person->name);
  }
  // if line has no tail, set the tail as the new person
  if (bank_line->tail == NULL) {
    bank_line->tail = new_person;
    printf("  👇 %s is the last person in the line\n", new_person->name);
  } else {
    // set the current tail's next as the new person
    bank_line->tail->next = new_person;
    // set the line's tail as the new person
    bank_line->tail = new_person;
    printf("  👇 %s went to the back of the line\n", new_person->name);
  }
}

// function to print the information of a person
void info(Person *person) {
  printf("  😃 \"My name is %s. I am %d years old. ", person->name, person->age);
  if (person->next != NULL) {
    printf("The person after me is %s\"\n", person->next->name);
  } else {
    printf("No one comes after me in the line\"\n");
  }
}

// function to print the information of all persons in the line
void bank_line_info(BankLine *bank_line) {
  printf("👀 This bank line is %s\n", bank_line->name);
  printf("👀 The person at the head of the line is %s (age %d years)\n",
         bank_line->head->name, bank_line->head->age);
  // set current person as the head of the line
  Person *current_person = bank_line->head;
  // as long as the current person is not NULL, print the information
  // of the current person and increment the current person to the next person
  while (current_person != NULL) {
    info(current_person);
    current_person = current_person->next;
  }
}

// function to clean up bank line from memory
void free_bank_line(BankLine *bank_line) {
  printf("👀 Freeing the line \"%s\"\n", bank_line->name);
  Person *current_person = bank_line->head;
  while (current_person != NULL) {
    Person *next = current_person->next;
    free(current_person);
    current_person = next;
  }
}

int main() {
  BankLine rb_line = create_bank_line("Reepooblic Bank Line");

  // add some persons to the line
  add_person_to_line("David", 17, &rb_line);
  add_person_to_line("Joash", 26, &rb_line);
  add_person_to_line("Athaliah", 18, &rb_line);
  add_person_to_line("Anita", 36, &rb_line);

  // print info on the line
  bank_line_info(&rb_line);
  // clear line from memory
  free_bank_line(&rb_line);

  return 0;
}