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#include "stack.h"
#include <stdlib.h>
// Create a new stack
struct stack *new_stack(int capacity)
{
struct stack *pt = (struct stack *)malloc(sizeof(struct stack));
pt->max_size = capacity;
pt->top = -1;
pt->items = (int *)malloc(sizeof(int) * capacity);
return pt;
}
// Add a new item to a stack
void stack_push(struct stack *pt, int x)
{
// Avoid a overflow by checking if the stack is full
if (pt->top == pt->max_size - 1)
err(0);
// Add an element and increase the top index
pt->items[++pt->top] = x;
}
// Get the topmost item of a stack
int stack_peek(struct stack *pt)
{
// Check if the stack is empty
if (pt->top == -1)
err(1);
return pt->items[pt->top];
}
// Remove the topmost item of a stack
int stack_pop(struct stack *pt)
{
// Check for a stack underflow
if (pt->top == -1)
err(0);
// Decrease the stack size by 1 and (optionally) return the popped element
return pt->items[pt->top--];
}
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