Learn and practice the Hash Maps, Knowing What to Track, Top K Elements, and the Heaps patterns to solve coding interview problems.

Grokking Grind 75 in Python: Mastery through Coding Patterns

Efficient data management, information tracking, element identification, and value optimization are crucial to problem-solving, particularly for challenges that involve handling, analyzing, and extracting meaningful insights from data. This module teaches essential coding patterns for all such coding challenges. It covers Hash Maps for storing and retrieving data, Knowing What to Track for identifying and managing key information, Top K Elements for extracting significant data points, and Heaps for efficiently handling extreme values in datasets. These techniques are valuable for solving various data-centric challenges, optimizing algorithms, and data manipulation.

Heaps, Hashing and Tracking

For the following strings, can we generate the ransom note using the letters from the magazine string?

ransom note = "problemsolving"

magazine = "adsoptendroblemfemopvinxtbml"

For the following strings, can we generate the ransom note using the letters from the magazine string?
ransom note = “problemsolving”
magazine = “adsoptendroblemfemopvinxtbml”

For the following strings, can we generate the ransom note using the letters from the magazine string?

ransom note = "codinginterviewquestions"

magazine = "aboincsdefoetingvqtniewonoregessnutins"

For the following strings, can we generate the ransom note using the letters from the magazine string?
ransom note = “codinginterviewquestions”
magazine = “aboincsdefoetingvqtniewonoregessnutins”

For the following strings, can we generate the ransom note using the letters from the magazine string?

ransom note = "youhaveakindheart"

magazine = "abecdefghiavjklmaonopqhrtuvweaxyz"




For the following strings, can we generate the ransom note using the letters from the magazine string?
ransom note = “youhaveakindheart”
magazine = “abecdefghiavjklmaonopqhrtuvweaxyz”

For the following strings, can we generate the ransom note using the letters from the magazine string?

ransom note = "youareagreathuman"

magazine = "eaartygamomneltrrouean"

For the following strings, can we generate the ransom note using the letters from the magazine string?
ransom note = “youareagreathuman”
magazine = “eaartygamomneltrrouean”

Ransom Note

Ransom Note

## 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.

> **Note:** As an additional challenge, we have intentionally hidden the solution to this puzzle. 

# 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: `can_construct`\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 `can_construct` 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 `can_construct`.\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) `can_construct`. \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) `can_construct`. \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:
        from collections import defaultdict

        def can_construct(ransom_note, magazine):

            # Create an empty hash map to store the frequency of each character in the magazine string
            char_frequency = {}
            
            for char in magazine:

                # Increase its count, if the character is already in the hash map
                # If the character is not in the hash map, add it with a frequency of 1
                char_frequency[char] = char_frequency.get(char, 0) + 1

            for char in ransom_note:

                # If the character is not in the char_frequency hash map or its count is 0, return False
                if char not in char_frequency or char_frequency[char] == 0:
                    return False

                # Otherwise, decrease the character's frequency count in the hash map by 1
                else:
                    char_frequency[char] -= 1
                    
            # The ransom note can be constructed from the magazine if the False is not returned yet
            return True
        """
        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
        """
        # multiple outputs will be added at each index respectively for a single test_case
        expected_outputs = []
        inp1 = self.__inputs[0]
        inp2 = self.__inputs[1]
        expected = can_construct(inp1 , inp2)
        # store the 1st expected output that should be displayed to the user 
        expected_outputs.append(expected)
        actual = self.__actual_outputs[0]
        if json.dumps(expected) == json.dumps(actual):
            self.__edu_result.store_result(expected_outputs, TestCaseResult.PASS)
        else:
            self.__edu_result.store_result(expected_outputs, TestCaseResult.FAIL)

        return self.__edu_result

def can_construct(ransom_note, magazine):

    # Replace this placeholder return statement with your code
    return False


PrivateTestCases.yaml

testcases:
  - name: "testcase 1"
    inputs:
    - 1 : codinginterviewquestions
    - 2 : aboincsdefoetingvqtniewonoregessnutins
    output: 
    - 1 : True
  - name: "testcase 2"
    inputs:
    - 1: code
    - 2: coingd
    output:
    - 1 : False
  - name: "testcase 3"
    inputs:
    - 1: codinginterview
    - 2: vieewidingcodinter
    output:
    - 1 : True
  - name: "testcase 4"
    inputs:
    - 1: program
    - 2: programming
    output:
    - 1 : True
  - name: "testcase 5"
    inputs:
    - 1: me
    - 2: meme
    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
 """
 import re
 # Inputs can be accessed using self.__inputs starting from 0 to len(self.__inputs) - 1
 if len(self.__inputs[0]) < 1 or len(self.__inputs[0]) > 100000:
 self.store_result("Length of 'ransom note' should be between 1 and 10^5.", ValidationFunction.FAIL)
 elif len(self.__inputs[1]) < 1 or len(self.__inputs[1]) > 100000:
 self.store_result("Length of 'magazine' should be between 1 and 10^5.", ValidationFunction.FAIL)
 elif not re.match(r'^[a-z]+$', self.__inputs[0]):
 self.store_result("Input1 'ransom note' should only have lowercase English alphabets.", ValidationFunction.FAIL)
 elif not re.match(r'^[a-z]+$', self.__inputs[1]):
 self.store_result("Input2 'magazine' should only have lowercase English alphabets.", ValidationFunction.FAIL)
 else:
 self.store_result("", ValidationFunction.PASS)

Hash Maps

Knowing What to Track

Top K Elements

Heaps

Conclusion

Ransom Note

Statement

Examples

Understanding the problem

Figure it out!

Try it yourself