Init commit

main.c

@@ -0,0 +1,106 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+struct List {
+    struct List *prev, *next;
+    int value;
+};
+
+struct List *init(int value);
+
+void add(struct List *list, int value);
+
+void rem(struct List **list, int value_to_remove);
+
+void print_list(const struct List *list);
+
+int main(void) {
+    struct List *seznam = init(1);
+    add(seznam, 5);
+    add(seznam, 2);
+    print_list(seznam);
+
+    rem(&seznam, 1);
+    print_list(seznam);
+
+    rem(&seznam, 2);
+    print_list(seznam);
+
+    rem(&seznam, 5);
+    print_list(seznam);
+
+    return 0;
+}
+
+struct List *init(const int value) {
+    struct List *list = malloc(sizeof(struct List));
+    list->next = nullptr;
+    list->prev = nullptr;
+    list->value = value;
+
+    return list;
+}
+
+void add(struct List *list, const int value) {
+    while (list->next != NULL) {
+        list = list->next;
+    }
+
+    struct List *alloc_list = init(value);
+    alloc_list->next = nullptr;
+    alloc_list->prev = list;
+    alloc_list->value = value;
+
+    list->next = alloc_list;
+}
+
+void rem(struct List **list, const int value_to_remove) {
+    struct List *first = *list;
+    // we need in case first element (which caller holds is destroyed), or there are no more elements (the list is destroyed)
+    struct List *it = *list;
+    struct List *next;
+
+    for (; it != NULL; it = next) {
+        next = it->next;
+        if (it->value != value_to_remove) continue;
+
+        // we have to remove this element
+        const bool has_prev = it->prev != NULL;
+        const bool has_next = it->next != NULL;
+
+        if (has_prev) {
+            // we have an element to the left
+            if (has_next) {
+                // we have an element to the right
+                it->prev->next = it->next;
+                it->next->prev = it->prev;
+            } else {
+                // we don't have an element to the right
+                it->prev->next = nullptr;
+            }
+        } else {
+            // we don't have an element to the left
+            // we can surmise this is the first element and caller will crash if they don't have the correct element
+            if (has_next) {
+                it->next->prev = nullptr;
+                first = it->next;
+            } else {
+                first = nullptr;
+            }
+        }
+
+        // free the memory taken by current element
+        free(it);
+    }
+
+    *list = first;
+}
+
+void print_list(const struct List *list) {
+    if (list == NULL) printf("Empty list");
+
+    for (; list != NULL; list = list->next) {
+        printf("%d ", list->value);
+    }
+    printf("\n");
+}