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#include <cgreen/cgreen.h>
/*
Design and implement a `MinStack` data structure that can store
comparable elements and supports the stack operations:
* `push(x)`
* `pop()`
* `size()`
* `min()`
All operations should run in constant time.
*/
Describe(MinStack);
BeforeEach(MinStack){ }
AfterEach(MinStack){ }
struct node {
int data;
struct node *next;
};
typedef struct node Node;
typedef struct {
Node *head;
} Stack;
static Stack *initialize() {
Stack *self = malloc(sizeof(Stack));
self->head = NULL;
return self;
}
static int size(Stack *self) {
Node *current = self->head;
int i;
for (i = 0; current != NULL; i++)
current = current->next;
return i;
}
static Node *new(int data) {
Node *node = malloc(sizeof(Node));
node->next = NULL;
node->data = data;
return node;
}
static int compare(int x, int y) {
return x == y ? 0 : (x > y) ? 1 : -1;
}
static void insert(Node **self, int data) {
int comparison = compare(data, (*self)->data);
Node *node = new(data);
switch(comparison) {
case 1:
if ((*self)->next)
insert(&((*self)->next), data);
else
(*self)->next = node;
break;
default:
node->next = *self;
*self = node;
break;
}
}
static void push(Stack *self, int data) {
if (self->head)
insert(&self->head, data);
else
self->head = new(data);
}
static int min(Stack *self) {
if (self && self->head)
return self->head->data;
return (int)NULL;
}
static int pop(Stack *self) {
if (!self->head)
return (int)NULL;
Node *current = self->head;
int data = current->data;
self->head = current->next;
current->next = NULL;
free(current);
return data;
}
Ensure(MinStack, when_empty) {
Stack *stack = initialize();
assert_that(size(stack), is_equal_to(0));
assert_that(min(stack), is_equal_to(NULL));
assert_that(pop(stack), is_equal_to(NULL));
free(stack);
}
Ensure(MinStack, when_pushing_a_single_integer) {
Stack *stack = initialize();
push(stack, 1);
assert_that(size(stack), is_equal_to(1));
assert_that(min(stack), is_equal_to(1));
assert_that(pop(stack), is_equal_to(1));
assert_that(size(stack), is_equal_to(0));
free(stack);
}
Ensure(MinStack, when_pushing_multiple_integers_out_of_order) {
Stack *stack = initialize();
push(stack, 2);
push(stack, 3);
push(stack, 1);
assert_that(size(stack), is_equal_to(3));
assert_that(min(stack), is_equal_to(1));
assert_that(pop(stack), is_equal_to(1));
assert_that(size(stack), is_equal_to(2));
assert_that(pop(stack), is_equal_to(2));
assert_that(size(stack), is_equal_to(1));
assert_that(pop(stack), is_equal_to(3));
assert_that(size(stack), is_equal_to(0));
assert_that(pop(stack), is_equal_to(NULL));
assert_that(size(stack), is_equal_to(0));
free(stack);
}
Ensure(MinStack, when_pushing_duplicate_values_on_to_the_stack) {
Stack *stack = initialize();
push(stack, 2);
push(stack, 1);
push(stack, 2);
assert_that(size(stack), is_equal_to(3));
assert_that(min(stack), is_equal_to(1));
assert_that(pop(stack), is_equal_to(1));
assert_that(pop(stack), is_equal_to(2));
assert_that(pop(stack), is_equal_to(2));
assert_that(pop(stack), is_equal_to(NULL));
free(stack);
}
TestSuite *min_stack_tests() {
TestSuite *suite = create_test_suite();
add_test_with_context(suite, MinStack, when_empty);
add_test_with_context(suite, MinStack, when_pushing_a_single_integer);
add_test_with_context(suite, MinStack, when_pushing_multiple_integers_out_of_order);
return suite;
}
|
