public class Stack: IStack
{
    private int[] s;

    public Stack(int N)
    {
        s = new int[N];
    }

    public void push(int x)
    {
        int i = 0;
        while (s[i] != 0)
        {
            ++i;
        }

        if (i+1 >= s.Length)
        {
            Array.Resize(ref s, s.Length*2);
        }

        s[i] = x;
    }

    public int pop()
    {
        int i = 0;

        while (i != s.Length && s[i] != 0)
        {
            i++;
        }

        s[i] = 0;
        return s[i - 1];
    }
}

I started to learn data structures. How can I improve my implementation? For example I don't now how to push 0 or how to realize my own resize?

I started to learn data structures. How can I improve my implementation? For example, I don't now how to push 0 or how to realize my own resize.

public class Stack: IStack
{
    private int[] s;

    public Stack(int N)
    {
        s = new int[N];
    }

    public void push(int x)
    {
        int i = 0;
        while (s[i] != 0)
        {
            ++i;
        }

        if (i+1 >= s.Length)
        {
            Array.Resize(ref s, s.Length*2);
        }

        s[i] = x;
    }

    public int pop()
    {
        int i = 0;

        while (i != s.Length && s[i] != 0)
        {
            i++;
        }

        s[i] = 0;
        return s[i - 1];
    }
}