HackerRank Nested Lists Python solution

Given the names and grades for each student in a Physics class of N 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 same grade, order their names alphabetically and print each name on a new line.

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, and the second line contains their grade.

Constraints

• 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 Physics; 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 5 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 37.2 belongs to Tina. The second lowest grade of 37.21 belongs to both Harry and Berry, so we order their names alphabetically and print each name on a new line.

Solution in Python3

Beginner friendly solution with comments

#take value of n
no_of_students = int(input())
#create empty list
records = []
#append record of each student name,score in a for loop
for i in range(no_of_students):
    name = input()
    score = float(input())
    records.append([name, score])

#convert list of records to a python dictionary
# [['Harry', 37.21], ['Berry', 37.21]] becomes 
# {'Harry': 37.21, 'Berry': 37.21}
records = dict(records)
#get only values from our dictionary and use set function to rmeove duplicate score then sort it in ascending order
scores = sorted(set(records.values()))
#index 1 has the 2nd lowest score
second_lowest_score = scores[1]
#create a list of names of students who has 2nd lowest score using list comprehension
second_lowest_students = [name for name,score in records if score==second_lowest_score]
#sort names in alphabetical order
second_lowest_students.sort()
#loop through each name and print
for name in second_lowest_students:
    print(name)

Beginner friendly solution without comments

no_of_students = int(input())
records = []
for i in range(no_of_students):
    name = input()
    score = float(input())
    records.append([name, score])
records = dict(records)
scores = sorted(set(records.values()))
second_lowest_score = scores[1]
second_lowest_students = [name for name,score in records if score==second_lowest_score]
second_lowest_students.sort()
for name in second_lowest_students:
    print(name)

Advanced users

students = [[input(),float(input())] for i in range(int(input()))]
second_highest = sorted(set(j for i,j in students))[1]
print("\n".join(sorted(i for i,j in students if j==second_highest)))