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

Educative-99 in Go: Accelerate Your Coding Interview Prep

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

# Statement
Given an array, _nums_, containing $n$ distinct numbers in the range $[0, n]$, return the only number in the range that is missing from the array.

**Constraints:**
- $n =$ `nums.length` 
- $1 \leq n \leq 10^3$
- $0 \leq$ `nums[i]` $\leq n$
- There are no duplicates in the array.

# 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 would be the output if the following array is given as input?

[0, 2, 4, 6, 7, 8, 3, 9, 5, 10]

What would be the output if the following array is given as input?
[0, 2, 4, 6, 7, 8, 3, 9, 5, 10]

What would be the output if the following array is given as input?

[0, 12, 4, 6, 7, 8, 3, 9, 5, 10, 2, 1]


What would be the output if the following array is given as input?
[0, 12, 4, 6, 7, 8, 3, 9, 5, 10, 2, 1]

What would be the output if the following array is given as input?

[0, 1, 2]

What would be the output if the following array is given as input?
[0, 1, 2]

Missing Number

Missing Number

# 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 `main.go` in the following coding playground. The supporting code template provided in `traversal.go` is meant to assist in developing your solution to the problem.


package main

import (
 "fmt"
)

// Template for array traversal

type Traversal struct {
 array []int
}

func (this *Traversal) forwardTraversal() {
 for _, element := range this.array{
 fmt.Print(element)
 }
} 

func (this *Traversal) backwardTraversal() {
 for i := len(this.array) - 1; i <= 0; i-- {
 fmt.Print(this.array[i])
 }
}

# 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: `findMissingNumber`\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 `findMissingNumber` 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 `findMissingNumber`.\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) `findMissingNumber`. \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) `findMissingNumber`. \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(find_missing_number(self.__inputs[0]))

 if json.dumps(find_missing_number(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 find_missing_number(nums):
 len_nums = len(nums)
 index = 0

 while index < len_nums:
 value = nums[index]

 if value < len_nums and value != nums[value]:
 nums[index], nums[value] = nums[value], nums[index]

 elif value >= len_nums:
 index+=1

 else:
 index += 1

 for x in range(len_nums):
 if x != nums[x]:
 return x
 return len_nums

package main

func findMissingNumber(nums []int) int {

  // Your code will replace this placeholder return statement
  return -1
}

private.yaml

testcases:
  - name: "testcase 1"
    inputs:
    - 1 : [0, 1, 2, 4]
    output: 
    - 1 : 3

  - name: "testcase 2"
    inputs:
    - 1: [3, 0, 1, 4]
    output:
    - 1 : 2
        
  - name: "testcase 3"
    inputs:
    - 1: [1, 4, 5, 6, 8, 2, 0, 7]
    output:
    - 1 : 3
        
  - name: "testcase 4"
    inputs:
    - 1: [1, 0, 2, 3, 4, 5, 6, 8, 9, 7, 11]
    output:
    - 1 : 10
        
  - name: "testcase 5"
    inputs:
    - 1: [1]
    output:
    - 1 : 0

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
 """
 # inputs can be accessed using self.__inputs starting from 0 to len(self.__inputs) - 1
 nums=self.__inputs[0]
 min_length=0
 max_length=len(nums)
 n=len(nums)
 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, int) and not isinstance(elem, bool) for elem in arr)
 # inputs can be accessed using self.__inputs starting from 0 to len(self.__inputs) - 1
 if not is_valid_1d_array(nums):
 self.store_result(("Invalid test case."), ValidationFunction.FAIL)
 elif len(nums) < 1 or len(nums) > 1000 :
 self.store_result ("Input length should be between 1 and 1000", ValidationFunction.FAIL)
 elif any(value < 0 or value > n for value in nums):
 self.store_result("All elements in the input set should be between 0 and array length", ValidationFunction.FAIL)
 elif len(nums) != len(set(nums)):
 self.store_result("Input should not have any duplicates", ValidationFunction.FAIL)
 else:
 self.store_result("", ValidationFunction.PASS)

Cyclic Sort

Topological Sort

Conclusion

Missing Number

Statement

Examples

Understand the problem

Figure it out!

Try it yourself