Learn and practice the Dynamic Programming pattern to solve coding interview problems.

Speedrun the Meta Coding Interview: Top Problems in Go

This module covers the most important problem-solving technique in the optimization domain: Dynamic Programming. In computer science, we often come across problems that have a well-defined structure, where the same subproblem is encountered and solved multiple times. Dynamic Programming allows us to compute once and reuse the solutions to recurring subproblems.

Optimization Techniques

What is the number of palindromic substrings in the string "car"?

What is the number of palindromic substrings in the string “car”?

What is the number of palindromic substrings in the string "noon"?

What is the number of palindromic substrings in the string “noon”?

What is the number of palindromic substrings in the string "rotator"?

What is the number of palindromic substrings in the string “rotator”?

# 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: `countPalindromicSubstrings`\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 `countPalindromicSubstrings` 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 `countPalindromicSubstrings`.\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) `countPalindromicSubstrings`. \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) `countPalindromicSubstrings`. \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.

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(count_palindromic_substrings(self.__inputs[0]))

        if json.dumps(count_palindromic_substrings(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 count_palindromic_substrings(s):
    count = 0

    dp = [[False for i in range(len(s))] for i in range(len(s))]
    
    for i in range(len(s)):
        dp[i][i] = True
        count += 1

    for i in range(len(s)-1):
        dp[i][i + 1] = (s[i] == s[i + 1])
        count += dp[i][i + 1]

    for length in range(3, len(s)+1):
        i = 0
        for j in range(length - 1, len(s)):
            dp[i][j] = dp[i + 1][j - 1] and (s[i] == s[j])
            count += dp[i][j]
            i += 1
    
    return count


package main

func countPalindromicSubstrings(s string) int {

	// Replace this placeholder return statement with your code

    return -1;
}


PrivateTestCases.yaml

testcases:
  - name: "testcase 1"
    inputs:
    - 1: "cat"
    output:
    - 1 : 3
  - name: "testcase 2"
    inputs:
    - 1 : "lever"
    output: 
    - 1 : 6
  - name: "testcase 3"
    inputs:
    - 1: "xyxxyz"
    output:
    - 1 : 9
  - name: "testcase 4"
    inputs:
    - 1: "wwwwwwwwww"
    output:
    - 1 : 55
  - name: "testcase 5"
    inputs:
    - 1: "tattarrattat"
    output:
    - 1 : 24

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
 """
 s=self.__inputs[0]
 # inputs can be accessed using self.__inputs starting from 0 to len(self.__inputs) - 1
 if not (1 <= len(s) <= 1000):
 self.store_result("Length of 's' should be between 1 and 1000", ValidationFunction.FAIL)
 elif " " in s and " " not in "".join(s.split()):
 self.store_result("'s' must not have spaces ", ValidationFunction.FAIL)
 elif not all(c.islower() for c in s):
 self.store_result("'s' should consist of only lowercase English letters", ValidationFunction.FAIL)

 else:
 self.store_result("", ValidationFunction.PASS)

Try to solve the Palindromic Substrings problem.


Palindromic Substrings

Try to solve the Palindromic Substrings problem.

Dynamic Programming

Conclusion

Palindromic Substrings

Statement

Examples

Understand the problem

Figure it out!

Try it yourself