Nested lists in python - HackerRank solution

Solution for hackerRank problem Nested lists in python

Problem :

Given the names and grades for each student in a class of students, store them in a nested list and print the name(s) of any student(s) having the second-lowest grade.

Note: If there are multiple students with the second lowest grade, order their names alphabetically and print each name on a new line.

Example

records=[ ["chi", 20.0], ["beta", 50.0], ["alpha", 50.0]

The ordered list of scores is [20.0, 50.0], so the second lowest score is 50.0 . There are two students with that score:  ["beta", "alpha"] . Ordered alphabetically, the names are printed as:

alpha
beta

Input Format

The first line contains an integer, N, the number of students.

The 2N subsequent lines describe each student over 2 lines.

- The first line contains a student's name.

- The second line contains their grade.

Constraints

• 2<=N<=5
• There will always be one or more students having the second lowest grade.

Output Format

Print the name(s) of any student(s) having the second lowest grade in. If there are multiple students, order their names alphabetically and print each one on a new line.

Sample Input 0

5

Harry

37.21

Berry

37.21

Tina

37.2

Akriti

41

Harsh

39

Sample Output 0

Berry

Harry

Explanation 0

There are  students in this class whose names and grades are assembled to build the following list:

python students = [['Harry', 37.21], ['Berry', 37.21], ['Tina', 37.2], ['Akriti', 41], ['Harsh', 39]]

The lowest grade of belongs toTina. The second lowest grade of belongs to both Harry and Berry, so we order their names alphabetically and print each name on a new line.

Procedure :

1. Start

2. Get the number of students (n)  as input from the user.

3. Loop from 0 to n

    Get the student name and mark as input from the user.

    Store the input in a dictionary as key-value pairs.

4. Store the scores of students (i.e. values of the dictionary) in a list.

5. Sort the list.

6. Remove the duplicate values in the list.

7. Second lowest mark is equal to the element at index 1 in the sorted list.

8. Print the corresponding name of the student.

9. End

Code :

#Getting the number of students from user

no_of_stu=int(input())

#Creating an empty dictionary

marksheet={}

#Storing the name as keys and its corresponding mark as values in the dictionary

for i in range(no_of_stu):

    name=str(input())

    mark=input()

    marksheet[name]=float(mark)

#Storing the marks in a list

score=list(marksheet.values())

#Sorting the list

score.sort()

#Removing duplicate elements in the list

unique_score=[]

for elt in score:

    if elt not in unique_score:

        unique_score.append(elt)

#Finding the second lowest mark

second_low=unique_score[1]

stu_name=[]

for names,marks in marksheet.items():

    if(marks==second_low):

        stu_name+=[names]

stu_name.sort()

for stu in stu_name:

    print(stu)

Explanation of the python functions used :

• values()- returns all the values in the dictionary.
• items()- returns all the keys and values in the dictionary as key value pair.
• append()- inserts the element at last of the list.
• sort()- sorts the list.

Related articles :

1. What's your name, Tuple - HackerRank solution in python

2. Finding the percentage in python - HackerRank solution

3. Athlete sort in python - HackerRank solution

4. Python HackerRank challenges with solution (Set 1)

5. HackerRank challenges with solutions (Rearrangement, Formula,

Word sorting, Numbers, Sentence)

6. Python exercise (Computing paradox, Rotate the matrix, Swap case,

First and last)

7. Python3 exercise - HackerRank solutions (Set 2)