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#include <stdio.h>
#include <stdlib.h>
#include "min_stack.h"
Stack *initialize() {
Stack *self = malloc(sizeof(Stack));
self->head = NULL;
return self;
}
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;
}
}
void push(Stack *self, int data) {
if (self->head)
insert(&self->head, data);
else
self->head = new(data);
}
int min(Stack *self) {
if (self && self->head)
return self->head->data;
return (int)NULL;
}
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;
}
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