lists.c

//
// Created by merlin on 4/4/2022.
//
#include <stdlib.h>
#include <stdio.h>
#include <stdbool.h>
#include "lists.h"

list_t *create_empty_list() {
    list_t *list = calloc(1, sizeof(list_t));
    //calloc will already have zeroed these, but this documents why the zeros are good
    list->head = NULL;
    list->tail = NULL;
    return list;
}

player_node *create_node(int player_id, int player_exp_points) {
    player_node *player = calloc(1, sizeof(player_node));
    player->player_id = player_id;
    player->player_exp_points = player_exp_points;
    player->next = NULL;
    return player;
}

void add_at_head(list_t *list, int player_id,
                 int player_exp_points) {
    player_node *player =
            create_node(player_id, player_exp_points);

    if (list->head != NULL) {
        player->next = list->head;
        list->head = player;
    } else {
        list->head = player;
        list->tail = player;
    }
}

void add_at_tail(list_t *list, int player_id,
                 int player_exp_points) {
    player_node *player =
            create_node(player_id, player_exp_points);

    if (list->head != NULL) {
        list->tail->next = player;
        list->tail = player;
    } else {
        list->head = player;
        list->tail = player;
    }
}

bool delete(list_t *list, int target_player_id) {
    player_node *curr = list->head;
    player_node *prev = NULL;
    while ((curr != NULL) && (curr->player_id != target_player_id)) {
        prev = curr;
        curr = curr->next;
    }
    if (curr == NULL) {
        // we didn't find what we were supposed to delete
        fprintf(stderr,
                "Tried to delete non-existent player id = %d\n", target_player_id);
        return false;
    }
    if (prev == NULL) {
        // deleting the head node
        list->head = list->head->next;
    } else {
        // deleting not at the head
        prev->next = curr->next;
        // fix up the tail pointer if we are deleting the last node
        if (curr == list->tail) {
            list->tail = prev;
        }
    }
    free(curr);
    return true;
}


player_node *find(list_t *list, int target_player_id) {
    player_node *p = list->head;
    while ((p != NULL) && (p->player_id != target_player_id)) {
        p = p->next;
    }
    return p;
}


void insert(list_t *list, int player_id, int player_exp_points) {
    player_node *player = create_node(player_id, player_exp_points);
    if (list->head != NULL) {
        player_node *curr = list->head;
        player_node *prev = NULL;
        while ((curr != NULL) && (curr->player_id < player_id)) {
            prev = curr;
            curr = curr->next;
        }
        if (prev == NULL) {
            // inserting at the head of the list
            player->next = list->head;
            list->head = player;
        } else if (curr == NULL) {
            // inserting at the tail of the list
            prev->next = player;
            list->tail = player;
        } else {
            // inserting in the middle of the list
            prev->next = player;
            player->next = curr;
        }

    } else {
        list->head = player;
        list->tail = player;
    }
}

void print_list(list_t *list) {
    player_node *p = list->head;
    if (p == NULL) {
        printf("The list is empty\n");
    }
    while (p != NULL) {
        printf("%d: %d\n", p->player_id, p->player_exp_points);
        p = p->next;
    }
}