stack_g.c

// C program for array implementation of stack 
#include <limits.h> 
#include <stdio.h> 
#include <stdlib.h> 

// A structure to represent a stack 
struct Stack { 
	int top; 
	unsigned capacity; 
	int* array; 
}; 

// function to create a stack of given capacity. It initializes size of 
// stack as 0 
struct Stack* createStack(unsigned capacity) 
{ 
	struct Stack* stack = (struct Stack*)malloc(sizeof(struct Stack)); 
	stack->capacity = capacity; 
	stack->top = -1; 
	stack->array = (int*)malloc(stack->capacity * sizeof(int)); 
	return stack; 
} 

// Stack is full when top is equal to the last index 
int isFull(struct Stack* stack) 
{ 
	return stack->top == stack->capacity - 1; 
} 

// Stack is empty when top is equal to -1 
int isEmpty(struct Stack* stack) 
{ 
	return stack->top == -1; 
} 

// Function to add an item to stack. It increases top by 1 
void push(struct Stack* stack, int item) 
{ 
	if (isFull(stack)) 
		return; 
	stack->array[++stack->top] = item; 
	printf("%d pushed to stack\n", item); 
} 

// Function to remove an item from stack. It decreases top by 1 
int pop(struct Stack* stack) 
{ 
	if (isEmpty(stack)) 
		return INT_MIN; 
	return stack->array[stack->top--]; 
} 

// Function to return the top from stack without removing it 
int peek(struct Stack* stack) 
{ 
	if (isEmpty(stack)) 
		return INT_MIN; 
	return stack->array[stack->top]; 
} 

// Driver program to test above functions 
int main() 
{ 
	struct Stack* stack = createStack(100); 

	push(stack, 10); 
	push(stack, 20); 
	push(stack, 30); 

	printf("%d popped from stack\n", pop(stack)); 

	return 0; 
}