CBSE 2025, Set 4, Q30 (a)

Question

A stack, named **`ClrStack`**, contains records of some colors. Each record is represented as a tuple containing four elements – **`ColorName`, `RED`, `GREEN`, `BLUE`**. **`ColorName`** is a string, and **`RED`, `GREEN`, `BLUE`** are integers. For example, a record in the stack may be `('Yellow', 237, 250, 68)`.

Write the following user-defined functions in Python to perform the specified operations on **`ClrStack`**:

**(i) `push_Clr(ClrStack, new_Clr)` :** This function takes the stack `ClrStack` and a new record `new_Clr` as arguments and pushes this new record onto the stack.

**(ii) `pop_Clr(ClrStack)` :** This function pops the topmost record from the stack and returns it. If the stack is already empty, the function should display the message "Underflow".

**(iii) `isEmpty(ClrStack)` :** This function checks whether the stack is empty. If the stack is empty, the function should return **`True`**, otherwise the function should return **`False`**.

Edvaya · Accepted Answer

The correct answer is Subjective. Here is the complete Python implementation for the required stack operations: ```python # (iii) Function to check if the stack is empty def isEmpty(ClrStack): if len(ClrStack) == 0: return True else: return False # (i) Function to push a new color record onto the stack def push_Clr(ClrStack, new_Clr): ClrStack.append(new_Clr) # (ii) Function to pop the topmost color record from the stack def pop_Clr(ClrStack): if isEmpty(ClrStack): print("Underflow") else: return ClrStack.pop() # --- Example Usage (Not required in the exam, but good for testing) --- # ClrStack = [] # push_Clr(ClrStack, ("Yellow", 237, 250, 68)) # push_Clr(ClrStack, ("Red", 255, 0, 0)) # print(pop_Clr(ClrStack)) # Output: ('Red', 255, 0, 0) # print(pop_Clr(ClrStack)) # Output: ('Yellow', 237, 250, 68) # pop_Clr(ClrStack) # Output: Underflow ``` **Explanation:** 1. **`isEmpty`:** Checks if the length of the list is 0. Returning boolean `True` or `False` simplifies checks in other functions. 2. **`push_Clr`:** Utilizes the built-in list method `.append()` to add the new tuple (`new_Clr`) to the top (end) of the stack. 3. **`pop_Clr`:** First calls the `isEmpty()` helper function to check for an underflow condition. If the stack has elements, it utilizes the built-in `.pop()` method to remove and return the last item added (LIFO).

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Computer Science > Computational Thinking And Programming 2 > Data Structures

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