Saturday, February 6, 2016

Implement Stack

Implement Stack

Implement a stack. You can use any data structure inside a stack except stack itself to implement it.

Example
push(1)
pop()
push(2)
top()  // return 2
pop()
isEmpty() // return true
push(3)
isEmpty() // return false


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class Stack {
    
    private ArrayList<Integer> stack = new ArrayList<Integer>();
    
    // Push a new item into the stack
    public void push(int x) {
        // Write your code here
        stack.add(x);
    }

    // Pop the top of the stack
    public void pop() {
        // Write your code here
        stack.remove(stack.size() - 1);
    }

    // Return the top of the stack
    public int top() {
        // Write your code here
        return stack.get(stack.size() - 1);
    }

    // Check the stack is empty or not.
    public boolean isEmpty() {
        // Write your code here
        return stack.size() == 0;
    }    
}
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