Learn and practice the Cyclic Sort and Topological Sort patterns to solve coding interview problems.

Speedrun the Netflix Coding Interview: Top Problems in Python

This module will focus on two advanced sorting algorithms, Cyclic Sort and Topological Sort. These are often used in coding interviews as a way to distinguish between average and outstanding candidates. Cyclic Sort may only be used if the input list meets certain criteria, and in those situations, it’s the most efficient sorting algorithm possible. Topological Sort utilizes graph-based algorithms to deal with partially ordered elements. This module teaches us to recognize whether either of these advanced sorting techniques is applicable, as well as how to use them to solve the given problem.

Advanced Sorting Techniques



**Constraints:**

- $1 \leq$ `words.length` $\leq 10^3$
- $1 \leq$ `words[i].length` $\leq 20$
- `order.length` $== 26$
- All the characters in `words[i]` and `order` are lowercase English letters.

# Examples


# Understand the problem

Let’s take a moment to make sure you’ve correctly understood the problem. The quiz below helps you check if you’re solving the correct problem:


What is the output if the following list of words and order are given as input?

words = ["alpha", "bravo", "charlie", "delta"]

order = "hlabcdgiwjkmnopqerstfuvxyz"

What is the output if the following list of words and order are given as input?
words = [“alpha”, “bravo”, “charlie”, “delta”]
order = “hlabcdgiwjkmnopqerstfuvxyz”

What is the output if the following list of words and order are given as input?

words = ["wrt", "wrf", "er", "ett", "rftt"]

order = "hlabcdgiwjkmnopqerstfuvxyz"

What is the output if the following list of words and order are given as input?
words = [“wrt”, “wrf”, “er”, “ett”, “rftt”]
order = “hlabcdgiwjkmnopqerstfuvxyz”

What is the output if the following list of words and order are given as input?

words = ["hello", "to", "my", "world"]

order = "hlabcdefgijkmnopqrstuvwxyz"

What is the output if the following list of words and order are given as input?
words = [“hello”, “to”, “my”, “world”]
order = “hlabcdefgijkmnopqrstuvwxyz”

What is the output if the following list of words and order are given as input?

words = ["you", "are", "a", "great", "human"]

order = "abcdefghijklmnopqrstuvwxyz"

What is the output if the following list of words and order are given as input?
words = [“you”, “are”, “a”, “great”, “human”]
order = “abcdefghijklmnopqrstuvwxyz”

Verifying an Alien Dictionary

Verifying an Alien Dictionary

# Figure it out!

We have a game for you to play. Rearrange the logical building blocks to develop a clearer understanding of how to solve this problem.

# Try it yourself

Implement your solution in the following coding playground:


# Quick Fix\nYou are Edward, a Senior Software Engineer who specializes in coding interview patterns, data structures and algorithms, and is great at debugging issues in code.\n\n- Edward, please keep in mind that you do not have to print the data of the placeholders. Also, do not mention anything about yourself.\n\nEdward, you are given the following data in the placeholders:\n- Function name: `verify_alien_dictionary`\n- Candidate's submitted solution code: USER_CODE\n- Error: ERROR_DESCRIPTION\n- Failed test case: FAILED_TEST_CASE\n- Coding language: `Python`\n\n- Edward, your task is to understand the type of error that is occurring in the coding language provided.\n- Once you've understood the error as per the error’s description, and why the test case failed, you will suggest how the candidate can improve their solution code to fix the error.\n- Edward, you will not give the corrected code, just a hint on what the error tells, and how to fix it.\n- Edward, please limit your response strictly to 100 words. No more words than the limit.

# Review Code\nEdward, your current task is to review the `verify_alien_dictionary` function(s) and the other function(s) invoked in it/them.\n\n-Take your time and review the candidate's solution code.\n- Do not review any extra/helper files or functions not invoked in the solution function `verify_alien_dictionary`.\n- Do not review the code of data structure objects instantiated like a binary tree, linked list, trie, union find, etc., in the solution functions. Just review the solution/algorithm function of the problem. \n- Also, if the solution code doesn’t use the coding pattern stated above, then please encourage the candidate to reattempt the problem using that pattern corectly.

# Review time complexity\n- Please provide a brief time complexity analysis of the function(s) `verify_alien_dictionary`. \n- While calculating time complexity, include the time complexity of built-in Python functions invoked by the code. \n- The answer should be to the point in approximately 60 words.

# Review space complexity\n- Please provide a brief space complexity analysis of the function(s) `verify_alien_dictionary`. \n- While calculating space complexity, include the space complexity of built-in Python functions invoked by the code. \n- Do not include the space used for the input parameters and the space used for just returning an output (not used as a scratch space). \n- The answer should be to the point in approximately 60 words.

def evaluate_results(self) -> object:
        """
        self.__inputs is the list of inputs that are passed as input to function
        self.__actual_output is a list of outputs that is produced by the learner's code
        return : self.__edu__result object
        """
        def verify_alien_dictionary(words, order):
            if len(words) == 1:
                return True
            
            order_map = {}
            
            for index, val in enumerate(order):
                order_map[val] = index
            
            for i in range(len(words) - 1):
                for j in range(len(words[i])):
                    if j >= len(words[i + 1]):
                        return False
                    
                    if words[i][j] != words[i + 1][j]:
                        if order_map[words[i][j]] > order_map[words[i + 1][j]]:
                            return False
                        break
            
            return True

        # multiple outputs will be added at each index respectively for a single test_case
        expected=verify_alien_dictionary(self.__inputs[0] ,self.__inputs[1])
        expected_outputs = [] 
        # store the 1st expected output that should be displayed to the user 
        expected_outputs.append(expected)

        if json.dumps(expected) == json.dumps(self.__actual_outputs[0]):
            self.__edu_result.store_result(expected_outputs, TestCaseResult.PASS)
        else:
            self.__edu_result.store_result(expected_outputs, TestCaseResult.FAIL)

        return self.__edu_result

def verify_alien_dictionary(words, order):
  
    # Replace this placeholder return statement with your code
    return False

PrivateTestCases.yaml

testcases:
  - name: "testcase 1"
    inputs:
    - 1 : ["h"]
    - 2 : hlabcdefgijkmnopqrstuvwxyz
    output: 
    - 1 : True
  - name: "testcase 2"
    inputs:
    - 1: ["martian"]
    - 2: mabcdefghijklnopqrstuvwxyz
    output:
    - 1 : True
  - name: "testcase 3"
    inputs:
    - 1: ["passengers", "to", "the", "unknown"]
    - 2: ptuabcdefghijklmnoqrsvwxyz
    output:
    - 1 : False
  - name: "testcase 4"
    inputs:
    - 1: ["jupyter", "ascending"]
    - 2: jabcdefghiklmnopqrstuvwxyz
    output:
    - 1 : True
  - name: "testcase 5"
    inputs:
    - 1: ["marvel", "marvellous"]
    - 2: marvelbcdfghijknopqstuwxyz
    output:
    - 1 : True


def sum(input_1, input_2):
    return input_1+input_2

def validate_inputs(self) -> None:
 """
 self.__inputs is the list of inputs that are passed as input to the function
 store the result using the self.store_result(error_msg, status)
 return: void
 """
 min_word_count = 1
 max_word_count = 1000
 min_word_length = 1
 max_word_length = 20
 valid_order_length = 26

 words = self.__inputs[0]
 order = self.__inputs[1]
 def is_valid_1d_array(arr):
 if not isinstance(arr, list):
 return False # Not a valid 1D array if it's not a list
 
 return all(isinstance(elem, str) and not isinstance(elem, bool) for elem in arr)

 if not is_valid_1d_array(words):
 self.store_result(("Invalid test case."), ValidationFunction.FAIL)
 # Inputs can be accessed using self.__inputs starting from 0 to len(self.__inputs) - 1
 elif any(num is None for num in words):
 self.store_result ("Not a valid test case", ValidationFunction.FAIL)
 elif not (min_word_count <= len(words) <= max_word_count):
 self.store_result("The number of words should be between 1 and 10^3.", ValidationFunction.FAIL)
 elif any(not isinstance(word, str) for word in words):
 self.store_result("Each 'word' should be a string.", ValidationFunction.FAIL)
 elif any(not (min_word_length <= len(word) <= max_word_length) for word in words):
 self.store_result("Each 'word' should have a length between 1 and 20.", ValidationFunction.FAIL)
 elif any(not word.islower() for word in words):
 self.store_result("Each 'word' should be a lowercase English word.", ValidationFunction.FAIL)
 elif any(not isinstance(char, str) or not char.islower() for char in order):
 self.store_result("Each character in 'order' should be a lowercase English letter.", ValidationFunction.FAIL) 
 elif len(order) != valid_order_length:
 self.store_result("The length of 'order' should be 26.", ValidationFunction.FAIL)
 else:
 self.store_result("", ValidationFunction.PASS)

Try to solve the Verifying an Alien Dictionary problem.

Cyclic Sort

Topological Sort

Conclusion

Verifying an Alien Dictionary

Statement

Examples

Understand the problem

Figure it out!

Try it yourself