Learn and practice the In-place Reversal of a Linked List, Stacks, and Matrices patterns to solve coding interview problems.

Grokking the Blind 75 Problems in JavaScript

Interviewers want to be sure that the candidate is comfortable manipulating linked lists, arrays, and data structures based on them, such as stacks and matrices. This module will provide the practice you need to review the concepts and techniques needed to solve common problems involving these data structures.

Basic Data Structures

# Statement
Given a string that may consist of opening and closing parentheses, your task is to check whether or not the string contains valid parenthesization.

The conditions to validate are as follows:
1) Every opening parenthesis should be closed by the same kind of parenthesis.  Therefore, `{)`and `[(])` strings are invalid.

2) Every opening parenthesis must be closed in the correct order.  Therefore, `)(` and `()(()` are invalid.

**Constraints:**

* $1 \leq$  `s.length` $\leq 10^3$
* The string will only contain the following characters: `(`, `)`, `[`, `]`, `{` and `}`.
# 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:

Are the parentheses in the following string valid or not?

"`(){}[]`"

Are the parentheses in the following string valid or not?
“<code>(){}[]</code>”

Are the parentheses in the following string valid or not?

"`{}[]{}[{}])`"

Are the parentheses in the following string valid or not?
“<code>{}[]{}[{}])</code>”

Valid Parentheses

Valid Parentheses

# 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. 

# 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: `isValid`\n- Candidate's submitted solution code: USER_CODE\n- Error: ERROR_DESCRIPTION\n- Failed test case: FAILED_TEST_CASE\n- Coding language: `JavaScript`\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 `isValid` 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 `isValid`.\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) `isValid`. \n- While calculating time complexity, include the time complexity of built-in JavaScript 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) `isValid`. \n- While calculating space complexity, include the space complexity of built-in JavaScript 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
        """
        # 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(is_valid(self.__inputs[0]))

        if json.dumps(is_valid(self.__inputs[0])) == 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 is_valid(string):
	dic = {")":"(", "}":"{", "]":"["}
	stack = []                          

	for i in string:
		if i in dic:
			if stack and stack[-1] == dic[i]:
				stack.pop()
			else:
				return False
		else:
			stack.append(i)
	
	if stack:
		return False
	return True

function isValid(s) {

    // Replace this placeholder return statement with your code
    return true;
}

export {
    isValid
}

PrivateTestCases.yaml

testcases:
  - name: "testcase 1"
    inputs:
    - 1 : "{}[]{}[{}])"
    output: 
    - 1 : False
  - name: "testcase 2"
    inputs:
    - 1 : "(){[{()}]}"
    output: 
    - 1 : True
  - name: "testcase 3"
    inputs:
    - 1 : "((((("
    output: 
    - 1 : False
  - name: "testcase 4"
    inputs:
    - 1 : "{{()}"
    output: 
    - 1 : False
  - name: "testcase 5"
    inputs:
    - 1 : "{()}}"
    output: 
    - 1 : False


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 function
 store the result using the self.store_result(error_msg, status)
 return : void
 """
 valid_chars = '(){}[]'
 # 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]) > 1000 :
 self.store_result (" 's' length should be between 1 and 1000", ValidationFunction.FAIL)
 elif any(char not in valid_chars for char in self.__inputs[0]):
 self.store_result("'s' should only have valid parentheses (),{},[]", ValidationFunction.FAIL)
 else:
 self.store_result("", ValidationFunction.PASS)

Try to solve the Valid Parentheses problem.


In-Place Manipulation of a Linked List

Stacks

Matrices

Conclusion

Valid Parentheses

Statement

Examples

Understand the problem

Figure it out!

Try it yourself