Learn and practice the Hash Maps and Knowing What to Track patterns to solve coding interview problems.

Speedrun the Microsoft Coding Interview: Top Problems in Go

Hash maps are powerful data structures that enable programmers to design more efficient solutions for certain problems. After practicing solving problems using hash maps, we will move to the more general problem-solving skill of figuring out the key characteristics of a problem, using various techniques to track them, in order to design remarkably efficient solutions for seemingly complex problems.

Hashing and Tracking

# Statement

Given a list of words or phrases, group the words that are anagrams of each other. An **anagram** is a word or phrase formed from another word by rearranging its letters.

**Constraints:**

Let `strs` be the list of strings given as input to find the anagrams.

- $1 \leq$ `strs.length` $\leq 10^3$
- $0 \leq$ `strs[i].length` $\leq 100$
- `strs[i]` consists of lowercase English letters.


> **Note:** The order in which the output is displayed doesn't matter.

What is the output if the following array is given as input?
 
['bat', 'tab', 'tan', 'at']



What is the output if the following array is given as input?
[‘bat’, ‘tab’, ‘tan’, ‘at’]

[['angel', 'angle', 'egal'],  ['study', 'dusty'], [glean'], ['night', 'thing']]

[['angel', 'glean', 'angle'], ['study', 'dusty'], ['night', 'thing'], ['egal']]

[['angel', 'glean', 'angle', 'egal'], ['study', 'dusty'], ['night', 'thing']]

[['angel', 'glean', 'angle', 'egal'], ['study', 'dusty'], ['night'], ['thing']]

What is the output if the following array is given as input?
 
['angel', 'study', 'glean', 'night', 'angle', 'thing', 'egal', 'dusty']

What is the output if the following array is given as input?
[‘angel’, ‘study’, ‘glean’, ‘night’, ‘angle’, ‘thing’, ‘egal’, ‘dusty’]

[['state', 'taste'], ['save', 'vase'], ['robed', 'bored', 'bore'], ['sat']]

[['state', 'taste', 'sat'], ['save', 'vase'], ['robed', 'bored', 'bore']]

[['state', 'taste', 'sat'], ['save', 'vase'], ['robed', 'bored'], ['bore']]

[['state', 'taste'], ['save', 'vase'], ['robed', 'bored'], ['sat'], ['bore']]

What is the output if the following array is given as input?
 
['state', 'save', 'robed', 'sat', 'taste', 'bored', 'vase', 'bore']

What is the output if the following array is given as input?
[‘state’, ‘save’, ‘robed’, ‘sat’, ‘taste’, ‘bored’, ‘vase’, ‘bore’]

Group Anagrams

Group Anagrams

## Try it yourself

Implement your solution in the following coding playground.

package main

func driverCode(arr []string) CustomClass {
    ds := new(CustomClass)
    ds.parsedData = groupAnagrams(arr)
    return *ds
}

# 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: `groupAnagrams`\n- Candidate's submitted solution code: USER_CODE\n- Error: ERROR_DESCRIPTION\n- Failed test case: FAILED_TEST_CASE\n- Coding language: `Go`\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 `groupAnagrams` 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 `groupAnagrams`.\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) `groupAnagrams`. \n- While calculating time complexity, include the time complexity of built-in Go 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) `groupAnagrams`. \n- While calculating space complexity, include the space complexity of built-in Go 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.

CustomClass

package main

import (
    "fmt"
    "os"
    "encoding/json"
)

type CustomClass struct {
    // class attributes
    parsedData [][]string
}

func (ds *CustomClass) generateError(data string) {
    fmt.Fprintln(os.Stderr, "Parsing Error: ", data, " in MyCustomDS is not parsable")
    os.Exit(-1)
}

func (ds *CustomClass) String() string {
    // override print() for your data structure
    return ""
}

// return value will be passed to user program
func (ds *CustomClass) Construct(value string, type_of_arr int) any {
    // parse test case in json string 'value' to your desired data structure
    json.Unmarshal([]byte(value), &ds.parsedData)
    return *ds
}

// input param contains return value of user program
func (ds *CustomClass) Traverse(input any, type_of_arr int) string {
    // convert your data structure 'input' to a json string representing a test case output
    cast, ok := input.(CustomClass)
    if !ok {
    }
    st, _ := json.Marshal(cast.parsedData)
    return string(st)
}

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
        """
        # multiple outputs will be added at each index respectively for a single test_case
        expected_outputs = [] 
        # store the 1st expected output that should be displayed to the user 
        expected_outputs.append(group_anagrams_test(self.__inputs[0]))

        if json.dumps(sorted(group_anagrams_test(self.__inputs[0]))) == json.dumps(sorted(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 dict_to_lst(subset):
        result = []
        if subset == []:
            return [[]]
        for dic in subset:
            result.append(list(dic))
        return result


def group_anagrams_test(strs):
    res = {}  # Hashmap for count
    for s in strs:
        count = [0] * 26  # A place for every single alphabet in our string
        # We will compute the frequency for every string
        for i in s:
            # Calculating the value from 1 to 26 for the alphabet
            index = ord(i) - ord('a')
            count[index] += 1  # Increasing its frequency in the hashmap
        # Each element in this tuple represents the frequency of an
        # English letter in the corresponding title
        key = tuple(count)
        if key in res:
            res[key].append(s)
        else:
            # We add the string as an anagram if it matched the content
            # of our res hashmap
            res[key] = [s]
    return dict_to_lst(res.values())


package main

func groupAnagrams(strs []string) [][]string {

    // Replace this placeholder return statement with your code
    return make([][]string, 0)
}


flatten_nested_list_iterator.yaml

testcases:
  - name: "testcase 1"
    inputs:
    - 1 : ["eat","tea","tan","ate","nat","bat"]
    output: 
    - 1 : [["eat", "tea", "ate"], ["bat"], ["tan", "nat"]]
  - name: "testcase 2"
    inputs:
    - 1: ["word", "sword", "drow", "rowd", "iced", "dice"]
    output:
    - 1 : [["word", "drow", "rowd"], ["sword"], ["iced", "dice"]]
  - name: "testcase 3"
    inputs:
    - 1 : ["eat", "drink", "sleep", "repeat"]
    output: 
    - 1 : [["eat"], ["drink"], ["sleep"], ["repeat"]]
  - name: "testcase 4"
    inputs:
    - 1: ["hello", "ohlle", "dark"]
    output:
    - 1 : [["hello", "ohlle"], ["dark"]]
  - name: "testcase 5"
    inputs:
    - 1: ["eat", "beat", "neat", "tea"]
    output:
    - 1 : [["eat", "tea"], ["beat"], ["neat"]]

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

def validate_inputs(self) -> None:
 """
 Validate the list of strings (strs) based on the given constraints.
 Store the result using self.store_result(error_msg, status).
 return: void
 """
 strs = self.__inputs[0]

 if not (1 <= len(strs) <= 10**3):
 self.store_result("Number of strings in 'strs' should be in the range 1 <= strs.length <= 10^3", ValidationFunction.FAIL)
 return

 for s in strs:
 if not (0 <= len(s) <= 100):
 self.store_result("String length in strs should be in the range 0 <= strs[i].length <= 100", ValidationFunction.FAIL)
 return

 elif not all(char.islower() for char in s):
 self.store_result("Each string in strs should consist of only lowercase English letters", ValidationFunction.FAIL)
 return

 self.store_result("", ValidationFunction.PASS)

Hash Maps

Knowing What to Track

Conclusion

Group Anagrams

Statement

Examples

Understand the problem

Figure it out!

Try it yourself