DSA

Stack Using Array

Stacks & Queues. Space O(n).

August 8, 2026

Practice Link

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.

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.

Solution#

cpp

class ArrayStack {
public:
    int* stackArray;
    int topIdx;
    int capacity;
    ArrayStack() {
        capacity = 10000;
        stackArray = new int[capacity];
        topIdx = -1;
    }
    
    void push(int x) {
        if(topIdx >= capacity){
            cout<<"Overflow"<<endl;
            return;
        }
        stackArray[++topIdx] = x;
    }
    
    int pop() {
        if(isEmpty()){
            return -1;
        }
        return stackArray[topIdx--];
    }
    
    int top() {
        if(isEmpty()){
            return -1;
        }
        return stackArray[topIdx];
    }
    
    bool isEmpty() {
        return topIdx==-1;
    }
};

Time Complexity:

push - O(1)

pop - O(1)

Space Complexity: O(n),

DSAImplement Queue using StacksStacks & Queues. Space O(n).DSANext Greater Element IISolution - Monotonic Stack approach. Optimal — Time O(2n), Space O(n).DSALargest Rectangle in a HistogramCovers: Brute Force, Using Stack, Optimal. Optimal — Time O(n), Space O(n).

Solution#

Related articles