Write an algorithm to find the second largest number in the given list

Python program to find second largest number in a list

Given a list of numbers, the task is to write a Python program to find the second largest number in the given list.
Examples:

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Python program to find second largest number in a list
Find Second largest element in an array
Python program to find second largest number in a list
Second Largest Number in Python
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Input: list1 = [10, 20, 4] Output: 10 Input: list2 = [70, 11, 20, 4, 100] Output: 70

Method 1: Sorting is an easier but less optimal method. Given below is an O(n) algorithm to do the same.

Python3

# Python program to find second largest
# number in a list
# list of numbers - length of 
# list should be at least 2

list1 = [10, 20, 4, 45, 99]

mx=max(list1[0],list1[1])

secondmax=min(list1[0],list1[1])

n =len(list1)

for i in range(2,n):

if list1[i]>mx:

secondmax=mx

mx=list1[i]

elif list1[i]>secondmax and \

mx != list1[i]:

secondmax=list1[i]

print("Second highest number is : ",\

str(secondmax))

Output Second highest number is : 45

Method 2: Sort the list in ascending order and print the second last element in the list.

Python3

# Python program to find largest
# number in a list
# list of numbers

list1 = [10, 20, 4, 45, 99]
# sorting the list
list1.sort()
# printing the second last element

print("Second largest element is:", list1[-2])

Output

Second largest element is: 45

Method 3: By removing the max element from the list

Python3

# Python program to find second largest
# number in a list
# list of numbers

list1 = [10, 20, 4, 45, 99]
# new_list is a set of list1

new_list = set(list1)
# removing the largest element from temp list

new_list.remove(max(new_list))
# elements in original list are not changed
# print(list1)

print(max(new_list))

Output 45

Method 4: Find max list element on inputs provided by the user

Python3

# Python program to find second largest
# number in a list
# creating empty list

list1 = []
# asking number of elements to put in list

num = int(input("Enter number of elements in list: "))
# iterating till num to append elements in list

for i in range(1, num + 1):

ele = int(input("Enter elements: "))

list1.append(ele)
'''
# sort the list 
list1.sort()

# print second maximum element
print("Second largest element is:", list1[-2])
'''
# print second maximum element using sorted() method

print("Second largest element is:", sorted(list1)[-2])

Output:

Enter number of elements in list: 4 Enter elements: 12 Enter elements: 19 Enter elements: 1 Enter elements: 99 Second Largest element is: 19

Method 5: Traverse once to find the largest and then once again to find the second largest.

Python3

def findLargest(arr):

secondLargest = arr[0]

largest = arr[0]

for i in range(len(arr)):

if arr[i] > largest:

largest = arr[i]

for i in range(len(arr)):

if arr[i] > secondLargest and arr[i] != largest:

secondLargest = arr[i]

return secondLargest

print(findLargest([10, 20, 4, 45, 99]))

Output:

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Find Second largest element in an array

Given an array of integers, our task is to write a program that efficiently finds the second largest element present in the array.
Example:

Input: arr[] = {12, 35, 1, 10, 34, 1} Output: The second largest element is 34. Explanation: The largest element of the array is 35 and the second largest element is 34 Input: arr[] = {10, 5, 10} Output: The second largest element is 5. Explanation: The largest element of the array is 10 and the second largest element is 5 Input: arr[] = {10, 10, 10} Output: The second largest does not exist. Explanation: Largest element of the array is 10 there is no second largest element

Python program to find second largest number in a list

In this tutorial, we will write a Python program to find the second largest number in a list. List is an ordered set of values enclosed in square brackets [ ]. List stores some values called elements in it, which can be accessed by their particular index. We will be following various approaches to find the second largest number in a list.

For a given list of numbers, the task is to find the largest number in the list.

Input: [11, 5, 2, 8, 4, 19]

Output: 11

Input: [2, 11, 18, 23, 6]

Output: 18

Second Largest Number in Python

When we have a lot of elements in our list, the thought of finding the highest or lowest element can come to our mind and Python has made it much easier for us.

In this article, we shall how we can use to find the second largest number in Python from a list.

Sorting the list and then print the second last number.
Removing the maximum element.
Finding the maximum element.
Traversing the list.

Let us have a look at the first approach-

Write an algorithm to find the second largest number in the given list

Python program to find second largest number in a list

Find Second largest element in an array

Python program to find second largest number in a list

Second Largest Number in Python

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