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deque.h
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deque.h
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#ifndef DEQUE_H_
#define DEQUE_H_
#include <stdlib.h>
#include <stdbool.h>
typedef struct DElem {
int val; // value pushed
void *next; // next DElem in deque
void *prev; // previous DElem in deque
bool is_empty; // only used for assertions right now. I might
// remove it at some point...
} DElem;
typedef struct Deque {
DElem *buff; // ptr to allocated memory
DElem *head; // ptr to head (front)
DElem *back; // ptr to back
DElem *empty_head; // ptr to empty-head (1st emtpy DElem)
DElem *empty_back; // ptr to empty-back (last empty DElem)
size_t count; // current number of pushed values
size_t capacity; // number of allocated DElems in buff
} Deque;
// prototypes
Deque deque_create(size_t n_elems);
void deque_destroy(Deque *deque);
void deque_push_front(Deque *deque, int val);
int deque_pop_front(Deque *deque);
void deque_push_back(Deque *deque, int val);
int deque_pop_back(Deque *deque);
int deque_front(Deque deque);
int deque_back(Deque deque);
void deque_print(Deque deque);
// implementations
#ifdef DEQUE_IMPLEMENTATION
#include <assert.h>
#define array_len(x) sizeof(x) / sizeof(*(x))
Deque deque_create(size_t n_elems)
{
Deque deque;
deque.buff = malloc(n_elems * sizeof *deque.buff);
if (deque.buff == NULL) {
fprintf(stderr, "Error: ['deque_create'] deque couldn't be allocated\n");
exit(1);
}
deque.head = NULL;
deque.back = NULL;
deque.count = 0;
deque.capacity = n_elems;
deque.empty_head = deque.buff;
deque.empty_back = deque.buff + deque.capacity - 1;
DElem *next;
DElem *prev;
for (size_t i = 0; i < deque.capacity; ++i) {
if (i < deque.capacity - 1) { // all but last elem
next = deque.buff + i + 1;
} else {
next = NULL;
}
if (i > 0) { // all but first elem
prev = deque.buff + i - 1;
} else {
prev = NULL;
}
deque.buff[i] = (DElem) {
.val = 0,
.next = next,
.prev = prev,
.is_empty = true
};
}
return deque;
}
void deque_destroy(Deque *deque)
{
if (deque->buff != NULL) {
free(deque->buff);
}
}
void __deque_grow(Deque *deque)
{
size_t realloc_inc_rate = 2;
size_t new_capacity = realloc_inc_rate * deque->capacity;
if ((deque->buff = realloc(deque->buff, new_capacity * sizeof(*deque->buff))) == NULL) {
printf("Error: ['__deque_grow'] deque buff couldn't be reallocated");
exit(1);
}
// initialize new elems as in deque_create
DElem *next;
DElem *prev;
for (size_t i = deque->capacity; i < new_capacity; ++i) {
if (i < new_capacity - 1) { // all but last elem
next = deque->buff + i + 1;
} else {
next = NULL;
}
if (i > deque->capacity) { // all but first elem
prev = deque->buff + i - 1;
} else {
prev = NULL;
}
deque->buff[i] = (DElem) {
.val = 0,
.next = next,
.prev = prev,
.is_empty = true
};
}
deque->empty_head = deque->buff + deque->capacity;
deque->empty_back = deque->buff + new_capacity - 1;
deque->capacity = new_capacity;
}
void __deque_shrink(Deque *deque)
{
int temp[deque->count];
DElem *next_head = deque->head;
for (size_t i = 0; i < deque->count && next_head != NULL; ++i) {
temp[i] = next_head->val;
next_head = next_head->next;
}
size_t realloc_shrink_rate = 2;
size_t new_capacity = deque->capacity / realloc_shrink_rate;
if ((deque->buff = realloc(deque->buff, new_capacity * sizeof(*deque->buff))) == NULL) {
printf("Error: ['__deque_shrink'] deque buff couldn't be reallocated");
exit(1);
}
deque->head = NULL;
deque->back = NULL;
deque->count = 0;
deque->capacity = new_capacity;
deque->empty_head = deque->buff;
deque->empty_back = deque->buff + deque->capacity - 1;
DElem *next;
DElem *prev;
for (size_t i = 0; i < deque->capacity; ++i) {
if (i < deque->capacity - 1) { // all but last elem
next = deque->buff + i + 1;
} else {
next = NULL;
}
if (i > 0) { // all but first elem
prev = deque->buff + i - 1;
} else {
prev = NULL;
}
deque->buff[i] = (DElem) {
.val = 0,
.next = next,
.prev = prev,
.is_empty = true
};
}
for (size_t i = 0; i < array_len(temp); ++i) {
deque_push_back(deque, temp[i]);
}
}
int deque_front(Deque deque)
{
if (deque.count <= 0) {
printf("Error: ['deque_front'] deque is emtpy");
exit(1);
}
return deque.head->val;
}
int deque_back(Deque deque)
{
if (deque.count <= 0) {
printf("Error: ['deque_back'] deque is emtpy");
exit(1);
}
return deque.back->val;
}
void deque_push_front(Deque *deque, int val)
{
if (deque->count == deque->capacity) __deque_grow(deque);
if (deque->count > 0) { // if deque not empty
assert(deque->empty_head->is_empty && "AssertionError: ['deque_push_front'] pushing to a non-empty DElem");
DElem *next_empty = deque->empty_head->next;
*deque->empty_head = (DElem) {
.val = val,
.next = deque->head,
.prev = NULL,
.is_empty = false
};
deque->head->prev = deque->empty_head; // prev head to point to new head loc
deque->head = deque->empty_head; // set new head loc
deque->empty_head = next_empty; // update empty
deque->count++;
} else { // if deque is empty
assert(deque->empty_head->is_empty && "AssertionError: ['deque_push_front'] pushing to a non-empty DElem");
DElem *next_empty = deque->empty_head->next;
*deque->empty_head = (DElem) {
.val = val,
.next = NULL,
.prev = NULL,
.is_empty = false
};
deque->head = deque->empty_head;
deque->back = deque->empty_head;
deque->empty_head = next_empty;
deque->count++;
}
if (deque->count == deque->capacity) deque->empty_back = NULL; // if pushed elem filled deque->buff
}
void deque_push_back(Deque *deque, int val)
{
if (deque->count == deque->capacity) __deque_grow(deque);
if (deque->count > 0) { // if deque not empty
assert(deque->empty_head->is_empty && "AssertionError: ['deque_push_front'] pushing to a non-empty DElem");
DElem *next_empty = deque->empty_head->next;
*deque->empty_head = (DElem) {
.val = val,
.next = NULL,
.prev = deque->back,
.is_empty = false
};
deque->back->next = deque->empty_head; // prev back to point to new back loc
deque->back = deque->empty_head; // set new backloc
deque->empty_head = next_empty; // update empty
deque->count++;
} else { // if deque is empty
assert(deque->empty_head->is_empty && "AssertionError: ['deque_push_front'] pushing to a non-empty DElem");
DElem *next_empty = deque->empty_head->next;
*deque->empty_head = (DElem) {
.val = val,
.next = NULL,
.prev = NULL,
.is_empty = false
};
deque->head = deque->empty_head;
deque->back = deque->empty_head;
deque->empty_head = next_empty;
deque->count++;
}
if (deque->count == deque->capacity) deque->empty_back = NULL; // if pushed elem filled deque->buff
}
int deque_pop_front(Deque *deque)
{
if (deque->head == NULL) {
fprintf(stderr, "Error: ['deque_pop_front'] deque is empty, can't pop\n");
exit(1);
}
int val = deque->head->val;
DElem *next_empty = deque->head;
if (deque->head == deque->back) deque->back = NULL; // if just one elem (empty is handled above)
deque->head = deque->head->next;
if (deque->head != NULL) deque->head->prev = NULL;
deque->count--;
*next_empty = (DElem) {
.val = 0,
.next = deque->empty_head,
.prev = NULL,
.is_empty = true
};
deque->empty_head->prev = next_empty;
deque->empty_head = next_empty;
if (deque->count <= deque->capacity / 4) __deque_shrink(deque);
return val;
}
int deque_pop_back(Deque *deque)
{
if (deque->back == NULL) {
fprintf(stderr, "Error: ['deque_pop_back'] deque is empty, can't pop\n");
exit(1);
}
int val = deque->back->val;
DElem *next_empty = deque->back;
if (deque->head == deque->back) deque->head = NULL;
deque->back = deque->back->prev;
if (deque->back != NULL) deque->back->next = NULL;
deque->count--;
*next_empty = (DElem) {
.val = 0,
.next = deque->empty_head,
.prev = NULL,
.is_empty = true
};
deque->empty_head->prev = next_empty;
deque->empty_head = next_empty;
if (deque->count <= deque->capacity / 4) __deque_shrink(deque);
return val;
}
void deque_print(Deque deque)
{
DElem *next = deque.head;
putc('[', stdout);
for (size_t i = 0; i < deque.count; i++) {
printf("%d", next->val);
next = next->next;
if (next != NULL) putc(' ', stdout);
}
puts("]\n");
}
#endif // DEQUE_IMPLEMENTATION
#endif // DEQUE_H_