stack1.c

#include <stdio.h>
#include <stdlib.h>
#include <limits.h>

struct Stack{
	int top;
	unsigned capacity;
	int* array;
};

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;
}

int isFull(struct Stack* stack){
	return stack->top == stack->capacity -1 ;
}

int isEmpty(struct Stack* stack){
	return stack->top == -1;
}

void push(struct Stack* stack, int item){
	if(isFull(stack))
		return;
	stack->array[++stack->top] = item;
}

int pop(struct Stack* stack){
	if(isEmpty(stack))
		return INT_MIN;
	return stack->array[stack->top--];
}

int peek(struct Stack* stack){
	if(isEmpty(stack))
		return INT_MIN;
	return stack->array[stack->top];
}

int main(){
	struct Stack* stack = createStack(100);
	//struct StackNode* root = NULL;
	
	push(stack,100);
	push(stack,20);

	printf(pop(stack));
	printf(peek(stack));
}