08 Stack --> 01 Implement stack using array

[FazeelUsmani]

Write a program to implement a Stack using Array. Your task is to use the class as shown in the comments in the code editor and complete the functions push() and pop() to implement a stack.

Example 1:

Input: push(2) push(3) pop() push(4) pop() Output: 3, 4 Explanation: push(2) the stack will be {2} push(3) the stack will be {2 3} pop() poped element will be 3, the stack will be {2} push(4) the stack will be {2 4} pop() poped element will be 4 Example 2:

Input: pop() push(4) push(5) pop() Output: -1, 5 Your Task: You are required to complete two methods push() and pop(). The push() method takes one argument, an integer 'x' to be pushed into the stack and pop() which returns an integer present at the top and popped out from the stack. If the stack is empty then return -1 from the pop() method.

Expected Time Complexity : O(1) for both push() and pop(). Expected Auixilliary Space : O(1) for both push() and pop().

Constraints: 1 <= Q <= 100 1 <= x <= 100

[logic-cribber]

Can I contribute to this problem ?

[FazeelUsmani]

Yeah, sure, @logic-cribber

[Aliwahid17]

// 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, 4);
    push(stack, 5);

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

    return 0;
}