Find the Second largest number of a nested list programme

Question

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

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

Below is my code for the above question :-

marks = sorted([student[i][1] for i in range(len(student))], reverse = True)

for num in range(1,len(marks)):
    if marks[num] < marks[0]:
        if marks[num+1] < marks[num]:
            temp = marks[num+1]
            break
    else:
        continue
second_top = [student[i] for i in range(len(student)) if student[i][1] == temp]

topper = sorted([k for k,l in second_top])

for i in range(len(topper)):
    print(topper[i])

Ouptut

Berry
Harry

Is there a way to improve this code. I’m a new to Python started practising on Hacker rank

Asked By: pquest

||

Source

Answer 1

Try this, which accounts for ex-aequos too:

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

scores = sorted(set([s[1] for s in students]))

students_by_score = {score: [student for student in students if student[1] == score] for score in scores}

second_bests = students_by_score[scores[1]]  # or whichever rank you want

print(second_bests)

Result:

[['Berry', 37.21], ['Harry', 37.21]]

Answered By: Cedric Druck

Answer 2

you could use a list comprehension with itertools.groupby and itertools.islice:

from itertools import groupby, islice

s = [i[0]  for e in islice((list(g) for k, g in groupby(sorted(students), key=lambda x: x[1])), 1, 2) for i in e]

print(*s, sep='n')

output:

Berry
Harry

another approach will be to store your data in a dict where the key will be the grade and the values will be a list with all the students that have the grade specified by the key:

from collections import defaultdict

grade_student = defaultdict(list)
for student, grade in students:
    grade_student[grade].append(student)

# second lowest grade   
second_grade = sorted(grade_student.keys())[1]

# order the names alphabetically and print each name on a new line
print(*sorted(grade_student[second_grade]), sep='n')

output:

Berry
Harry

Answered By: kederrac

Answer 3

First of all, I would sort the grades y ascending order:

>>> students = [['Harry', 37.21], ['Berry', 37.21], ['Tina', 37.2], ['Akriti', 41], ['Harsh', 39]]
>>> grades = sorted(set(g for _, g in students))
>>> grades
[37.2, 37.21, 39, 41]

The line set(g for _, g in students) extract the grades and remove the duplicates (set).

Then take the second element of the list, which is the second lowest grade:

>>> second_lowest_grade = grades[1]
>>> second_lowest_grade
37.21

And then loop on ordered names (alpabetically) for students having the second lowest grade:

>>> for name in sorted(n for n, g in students if g == second_lowest_grade):
...     print(name)
... 
Berry
Harry

Answered By: jferard

Answer 4

A newbie way to do it: Clears all the tests!!!

listb=[] (creating an empty list)
n=int(input()) (number of items in list)

for i in range(n): (loop initiated for creating a list A with names)
    lista=[]
    name = input()
    lista.append(name)

    for j in range (1): (loop for entering the score in list a, and making list b)
        score = float(input())
        lista.append(score)
        listb.append(lista)

listc=sorted(listb, key=lambda i: i[1]) (sort the list)
minx=min(listc, key=lambda i: i[1]) (taking minimum value)
second_minimum_score = max(listc, key=lambda i: i[1]>minx[1]) (extracting second minimum value)
my_value=second_minimum_score[1]
chaapo=[] (this list will contain our answer)
for i in range(len(listc)):
    if listc[i][1]==my_value:
      chaapo.append(listc[i][0])
    
y=sorted(chaapo)

for i in range (len(y)): (loop for printing, if there are multiple names)
    print(y[i])

Answered By: Shoaib Mansoor

Find the Second largest number of a nested list programme

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