Post Compare

TIP102 Unit 3 Session 1 (Click for link to problem statements)

U-nderstand

Understand what the interviewer is asking for by using test cases and questions about the problem.

• Q: How should the # character be handled?
  • A: The # character represents a backspace, so the previous character (if any) should be removed.
• Q: What should happen if there are multiple # characters?
  • A: Each # should remove one preceding character. If there is no character to remove, the text remains unchanged.
• Q: How should the drafts be compared?
  • A: After processing the drafts by applying the backspaces, the resulting strings should be compared to determine if they are equal.

P-lan

Plan the solution with appropriate visualizations and pseudocode.

General Idea: Use a stack to simulate the typing process, accounting for backspaces, and then compare the final processed strings.

1. Define a helper function `build_final_string(draft)` that processes the draft:
   1. Initialize an empty stack.
   2. Iterate through each character in the draft:
      1. If the character is `#`, pop the top character from the stack (if the stack is not empty).
      2. Otherwise, push the character onto the stack.
   3. Join the stack's characters into a string and return it as the final processed string.
2. In the main function `post_compare`, call `build_final_string` on both `draft1` and `draft2`.
3. Compare the resulting processed strings:
   1. If they are equal, return `True`.
   2. Otherwise, return `False`.

⚠️ Common Mistakes

• Forgetting to handle consecutive # characters properly.
• Not checking whether the stack is empty before attempting to pop a character.
• Comparing drafts directly without processing backspaces.

I-mplement

def build_final_string(draft):
    stack = []
    for char in draft:
        if char == '#':
            if stack:
                stack.pop()  # Simulate backspace
        else:
            stack.append(char)  # Add the character to the stack
    return ''.join(stack)

def post_compare(draft1, draft2):
    # Build the final strings after considering backspaces
    final_draft1 = build_final_string(draft1)
    final_draft2 = build_final_string(draft2)
    
    # Compare the resulting strings
    return final_draft1 == final_draft2