Let's get your stack reversal working correctly. Based on your test case and expected output, the issue is almost certainly that your existing reverse method is either modifying the entire underlying array (including empty placeholder positions) or not properly targeting only the active stack elements.

Correct Implementation of reverse(obj) #

Assuming your CStack class uses:

• obj.stack: The underlying array storing stack elements (with empty placeholders at the end)
• obj.top: An integer tracking the index of the top element (so valid elements are obj.stack(1:obj.top))

Here's the corrected method:

function reverse(obj)
    % REVERSE Reverses the order of elements in the stack
    % Check if stack is empty first - no action needed
    if obj.empty()
        return;
    end
    
    % Extract only the active elements (from bottom to top of the stack)
    active_elements = obj.stack(1:obj.top);
    
    % Reverse the active elements
    reversed_elements = flip(active_elements);
    
    % Replace the active portion of the stack with reversed elements
    obj.stack(1:obj.top) = reversed_elements;
end

Why This Works #

1. Empty Stack Check: Handles the edge case where reversing an empty stack should do nothing (matches your third test case where s1.empty() followed by reverse() still shows "The stack is empty").
2. Target Active Elements: We only work with obj.stack(1:obj.top) — this avoids modifying the empty placeholder positions in your array (which was likely causing incorrect output in your original code).
3. Proper Reversal: Using flip() reverses the order of the active elements, turning the original bottom-to-top sequence into the reversed bottom-to-top sequence (exactly what your test case expects).

Verification Against Your Test Case #

Let's walk through your test steps to confirm:

1. Initial Stack: s1 = CStack({1,2,3,'GGG'}) → active elements are [1,2,3,'GGG'] (bottom to top). After reverse(), they become ['GGG',3,2,1] — which matches your first expected output.
2. Push 5: Adds 5 to the top, making active elements ['GGG',3,2,1,5]. Reversing gives [5,1,2,3,'GGG'] — which matches your second expected output.
3. Empty Stack: After s1.empty(), obj.top is 0. The reverse() method checks for empty and does nothing, so the stack remains empty — matching your third expected output.

If Your CStack Uses a Different Internal Structure #

If your CStack stores the top element at the start of the array (instead of the end of the active portion), adjust the logic to target obj.stack(obj.top:end) instead, but based on your expected output, the above implementation should be the right fix.

内容的提问来源于stack exchange，提问作者topzeramail