Hacker Rank Python Challenges

Python Version 3

Problems

  1. List Comprehensions
  2. Find the Runner-Up Score!
  3. Nested Lists
  4. Finding the percentage
  5. Lists
  6. Tuples

List Comprehensions

Problem -> URL
Difficulty Level: Easy

Pseudocode:

  1. Read input from user.
  2. Create a empty list.
  3. For each combination on x, y and z check sum not equal to n. If true, append the pair to the list.
  4. Finally print the list

Solution:

def solution(x, y, z, n):
    result = []
    for i in range(0, x + 1):
        for j in range(0, y + 1):
            for k in range(0, z + 1):
                if (i + j + k != n):
                    result.append([i, j, k])
    print(result)


if __name__ == '__main__':
    x = int(input())
    y = int(input())
    z = int(input())
    n = int(input())
    solution(x,y,z,n)

Find the Runner-Up Score!

Problem -> URL
Difficulty Level: Easy

Pseudocode:

  1. Read input from user.
  2. Validate user input, constraints 2 <= n <= 10 and -100 <= score[i] <= 100.
  3. define two variable first_max and second_max with any minimum value less than -100.
  4. Iterate through score, for each score check,
    • if score is greater that first_max then we need to update second_max = first_max and update first_max = score.
    • else if score is greater than second_max and less than first_max then we need to update second_max with score.
    • else do nothing
  5. Finally, return second_max

Solution:

def is_valid_input(n, scores):
    if(n != len(scores)):
        return False
    if(n >= 2 and n <= 10):
        for score in scores:
            if(score < -100 or score > 100):
                return False
        return True
    return False
    

def solution(n, scores):
    if(is_valid_input(n, scores)):
        first_max = -101
        second_max = -101
        for score in scores:
            if (score > first_max):
                first_max, second_max = score, first_max
            elif(score > second_max and score < first_max):
                second_max = score
        print(second_max)


if __name__ == '__main__':
    n = int(input())
    arr = list(map(int, input().split()))
    solution(n, arr)

Nested Lists

Problem -> URL
Difficulty Level: Easy

Pseudocode:

  1. Read input from user.
  2. Validate user input, constraints 2 <= N <= 5.
  3. Crete a empty dict.
  4. define two variable first_min and second_min with any maximum value, here I used 10 ^ 5.
  5. Iterate through student records, for each record,
    • Considering score as key, store student names as list for each scores in the dict
    • Find the second minimum score,
      • If score < first_min, then assign first_min = score and second_min = first_min
      • else if score > first_min and score < second_min, then assign second_min = score
  6. Finally, get the names from dict for the second_min score from the dict.
  7. Sort the name and print as string with next line character for each name.

Solution:

def is_valid_input(records):
    num_records = len(records)
    if(num_records >= 2 and num_records <= 5):
        return True
    return False


def solution(records):
    if(is_valid_input(records)):
        names = {}
        first_min = 10 ** 5
        second_min = 10 ** 5
        for record in records:
            # Create dict of scores with all names associated to scores.
            score = record[1]
            name = record[0]
            if score in names:
                names[score].append(name)
            else:
                names[score] = [name]
            # Find Second Min Score
            if score < first_min:
                first_min, second_min = score, first_min
            elif score > first_min and score < second_min:
                second_min = score
        print("\n".join(sorted(names[second_min])))


if __name__ == '__main__':
    records = []
    for _ in range(int(input())):
        name = input()
        score = float(input())
        records.append([name, score])
    solution(records)

Finding the percentage

Problem -> URL
Difficulty Level: Easy

Pseudocode:

  1. Read input from user.
  2. Validate user input, constraints 2 <= n <= 10, 0 <= marks[i] <= 100 and len(marks) == 3.
  3. Calculate average mark for given student name.
  4. Print the average with 2digit precision.

Solution:

def is_valid_input(students):
    records_length = len(students)
    if (records_length >= 2 and records_length <= 10):
        for k,v in students.items():
            if(len(v) != 3):
                return False
            if(not(all(map(lambda x: x >= 0 and x <= 100, v)))):
                return False
        return True
    return False


def solution(students, name):
    if(is_valid_input(students)):
        average = sum(students[name])/len(students[name])
        print("{:.2f}".format(float(average)))


if __name__ == '__main__':
    n = int(input())
    student_marks = {}
    for _ in range(n):
        name, *line = input().split()
        scores = list(map(float, line))
        student_marks[name] = scores
    query_name = input()
    solution(student_marks, query_name)

Lists

Problem -> URL
Difficulty Level: Easy

Pseudocode:

  1. Read input from user.
  2. Create an empty list.
  3. For each user input, Based on type of list operation, call builtin list operations with required parameters and we need to cast the string input to int before storing it in the list.

Solution:

def solution(n):
    nums = []
    for i in range(0, n):
        user_input = str(input()).split(" ")
        operation = user_input[0]
        if(operation.lower() == "insert"):
            index = int(user_input[1])
            value = int(user_input[2])
            nums.insert(index, value)
        elif(operation.lower() == "print"):
            print(nums)
        elif(operation.lower() == "remove"):
            value = int(user_input[1])
            nums.remove(value)
        elif(operation.lower() == "append"):
            value = int(user_input[1])
            nums.append(value)
        elif(operation.lower() == "sort"):
            nums = sorted(nums)
        elif(operation.lower() == "pop"):
            nums.pop()
        elif(operation.lower() == "reverse"):
            nums.reverse()


if __name__ == '__main__':
    N = int(input())
    solution(N)

Tuples

Problem -> URL
Difficulty Level: Easy

Pseudocode:

  1. Read input from user.
  2. Convert list to tuple.
  3. Print the hash string for tuple using inbuilt function hash().

Solution:

def solution(nums):
    print(hash(tuple(nums)))


if __name__ == '__main__':
    n = int(input())
    integer_list = map(int, input().split())
    solution(integer_list)