Problem: Remove Consecutive Duplicates Given a string s, remove all consecutive duplicate characters and return the resulting string. Input Format A single line containing a string s (1 ≤ length of s ≤ 1000) The string will contain only lowercase English letters. Output Format Print the string after removing consecutive duplicate characters. Sample Input 1 aabbccddeee Sample Output 1 abcde Sample Input 2 aabaaabb Sample Output 2 abab
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Can you ask me a (that may be simple at rating of about 3/10) coding problem that tests problem solving skills of the candidate?
Sure! Here's a simple (3/10 difficulty) coding problem that tests basic problem-solving, string handling, and logic skills:
✅ Problem: Remove Consecutive Duplicates
Given a string s, remove all consecutive duplicate characters and return the resulting string.
🔹 Input Format
-
A single line containing a string
s(1 ≤ length of s ≤ 1000) -
The string will contain only lowercase English letters.
🔹 Output Format
-
Print the string after removing consecutive duplicate characters.
🔹 Sample Input 1
🔹 Sample Output 1
🔹 Sample Input 2
🔹 Sample Output 2
🧠 What it tests
-
Understanding of string traversal
-
Use of conditionals
-
Handling edge cases like repeated or single characters
Let me know when you're ready for the solution or hints!
Can you critique this rough algo:
s = "afafasgggewrtdg"
t = ""
last_seen_character = ''
streak_found = False
for c in s:
if c not in t:
t += c
last_seen_character = c
elif c in t and last_seen_character == c:
streak_found = True
last_seen_character = c
continue
else (c in t) and last_seen_character != c and not streak_found:
t += c
last_seen_character = c
streak_found = False
Thanks for sharing your rough algorithm! You're clearly thinking through the logic and edge cases, which is great. Let’s break down the approach and evaluate it step by step.
🔍 Your Goal:
You want to remove consecutive duplicate characters from a string.
✅ What’s good in your approach:
-
Tracking state: You're maintaining
last_seen_character— that’s useful for detecting consecutive repeats. -
Use of flags: You introduced
streak_foundto handle streaks, though it's a bit more complex than needed for this problem. -
Good intent: You’re trying to avoid adding characters that have already been added if they’re part of a consecutive streak.
❌ Issues in the Logic:
-
Wrong check for character presence in
t:-
You’re checking
if c not in t, but this checks if the character has ever occurred int, not if it's the same as the previous one. -
This can cause issues with strings like
"aabaaabb"— you'll incorrectly skip valid characters.
-
-
Incorrect
elsecondition:-
Python syntax error:
else (c in t) and ...is invalid. -
elsedoesn’t take a condition. You’d need to useelifagain.
-
-
Unnecessary use of
streak_found:-
You don’t need a
streak_foundflag. You only need to compare each character to the one immediately before it.
-
-
Adding characters that are not duplicates but previously seen:
-
You're preventing characters from being added again even if they're not consecutive — which is incorrect.
-
✅ Correct Logic Should Be:
Keep the character only if it’s not equal to the previous character.
✔️ Cleaned Up Version of the Algorithm:
🧪 Example:
Input: "aabaaabb"
Output: "abab"
⏱️ Time Complexity: O(n)
You visit each character once.
📦 Space Complexity: O(n)
In the worst case, the output string could be the same length as input.
🧠 Final Thoughts:
You're on the right track with tracking characters, but overcomplicating it with multiple conditions and flags. Stick to comparing only the current and previous characters — that’s sufficient here.
Let me know if you want to walk through more test cases or edge conditions!
So The Solution Is:
s = "afafasgggewrtdg"
t = ""
last_seen_character = None
for c in s:
if c != last_seen_character:
t += c
last_seen_character = c
print(t)
