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:
Method 1: Sorting is an easier but less optimal method. Given below is an O(n) algorithm to do the same.
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# 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))
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Method 2: Sort the list in ascending order and print the second last element in the list.
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# 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])
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Second largest element is: 45
Method 3: By removing the max element from the list
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# 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))
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Method 4: Find max list element on inputs provided by the user
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# 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])
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Output:
Enter number of elements in list: 4 Enter elements: 12 Enter elements: 19 Enter elements: 1 Enter elements: 99 Second Largest element is: 19Method 5: Traverse once to find the largest and then once again to find the second largest.
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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]))
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Output:
45Find the maximum elements in the first and the second halves of the Array
Given an array arr[] of N integers. The task is to find the largest elements in the first half and the second half of the array. Note that if the size of the array is odd then the middle element will be included in both halves.
Examples:
Input: arr[] = {1, 12, 14, 5}
Output: 12, 14
First half is {1, 12} and the second half is {14, 5}.
Input: arr[] = {1, 2, 3, 4, 5}
Output: 3, 5
Approach: Calculate the middle index of the array as mid = N / 2. Now the first halve elements will be present in the subarray arr[0…mid-1] and arr[mid…N-1] if N is even.
If N is odd then the halves are arr[0…mid] and arr[mid…N-1]
Below is the implementation of the above approach:
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// C++ implementation of the approach
#include <bits/stdc++.h>
using namespace std;
// Function to print largest element in
// first half and second half of an array
void findMax(int arr[], int n)
{
// To store the maximum element
// in the first half
int maxFirst = INT_MIN;
// Middle index of the array
int mid = n / 2;
// Calculate the maximum element
// in the first half
for (int i = 0; i < mid; i++)
maxFirst = max(maxFirst, arr[i]);
// If the size of array is odd then
// the middle element will be included
// in both the halves
if (n % 2 == 1)
maxFirst = max(maxFirst, arr[mid]);
// To store the maximum element
// in the second half
int maxSecond = INT_MIN;
// Calculate the maximum element
// int the second half
for (int i = mid; i < n; i++)
maxSecond = max(maxSecond, arr[i]);
// Print the found maximums
cout << maxFirst << ", " << maxSecond;
}
// Driver code
int main()
{
int arr[] = { 1, 12, 14, 5 };
int n = sizeof(arr) / sizeof(arr[0]);
findMax(arr, n);
return 0;
}
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// Java implementation of the approach
import java.io.*;
class GFG
{
static void findMax(int []arr, int n)
{
// To store the maximum element
// in the first half
int maxFirst = Integer.MIN_VALUE;
// Middle index of the array
int mid = n / 2;
// Calculate the maximum element
// in the first half
for (int i = 0; i < mid; i++)
{
maxFirst = Math.max(maxFirst, arr[i]);
}
// If the size of array is odd then
// the middle element will be included
// in both the halves
if (n % 2 == 1)
{
maxFirst = Math.max(maxFirst, arr[mid]);
}
// To store the maximum element
// in the second half
int maxSecond = Integer.MIN_VALUE;
// Calculate the maximum element
// int the second half
for (int i = mid; i < n; i++)
{
maxSecond = Math.max(maxSecond, arr[i]);
}
// Print the found maximums
System.out.print(maxFirst + ", " + maxSecond);
// cout << maxFirst << ", " << maxSecond;
}
// Driver Code
public static void main(String[] args)
{
int []arr = { 1, 12, 14, 5 };
int n = arr.length;
findMax(arr, n);
}
}
// This code is contributed by anuj_67..
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# Python3 implementation of the approach
import sys
# Function to print largest element in
# first half and second half of an array
def findMax(arr, n) :
# To store the maximum element
# in the first half
maxFirst = -sys.maxsize - 1
# Middle index of the array
mid = n // 2;
# Calculate the maximum element
# in the first half
for i in range(0, mid):
maxFirst = max(maxFirst, arr[i])
# If the size of array is odd then
# the middle element will be included
# in both the halves
if (n % 2 == 1):
maxFirst = max(maxFirst, arr[mid])
# To store the maximum element
# in the second half
maxSecond = -sys.maxsize - 1
# Calculate the maximum element
# int the second half
for i in range(mid, n):
maxSecond = max(maxSecond, arr[i])
# Print the found maximums
print(maxFirst, ",", maxSecond)
# Driver code
arr = [1, 12, 14, 5 ]
n = len(arr)
findMax(arr, n)
# This code is contributed by ihritik
|
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// C# implementation of the approach
using System;
class GFG
{
static void findMax(int []arr, int n)
{
// To store the maximum element
// in the first half
int maxFirst = int.MinValue;
// Middle index of the array
int mid = n / 2;
// Calculate the maximum element
// in the first half
for (int i = 0; i < mid; i++)
{
maxFirst = Math.Max(maxFirst, arr[i]);
}
// If the size of array is odd then
// the middle element will be included
// in both the halves
if (n % 2 == 1)
{
maxFirst = Math.Max(maxFirst, arr[mid]);
}
// To store the maximum element
// in the second half
int maxSecond = int.MinValue;
// Calculate the maximum element
// int the second half
for (int i = mid; i < n; i++)
{
maxSecond = Math.Max(maxSecond, arr[i]);
}
// Print the found maximums
Console.WriteLine(maxFirst + ", " + maxSecond);
// cout << maxFirst << ", " << maxSecond;
}
// Driver Code
public static void Main()
{
int []arr = { 1, 12, 14, 5 };
int n = arr.Length;
findMax(arr, n);
}
}
// This code is contributed by nidhiva
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// javascript implementation of the approach
function findMax(arr, n)
{
// To store the maximum element
// in the first half
var maxFirst = Number.MIN_VALUE
// Middle index of the array
var mid = n / 2;
// Calculate the maximum element
// in the first half
for (var i = 0; i < mid; i++)
{
maxFirst = Math.max(maxFirst, arr[i]);
}
// If the size of array is odd then
// the middle element will be included
// in both the halves
if (n % 2 == 1)
{
maxFirst = Math.max(maxFirst, arr[mid]);
}
// To store the maximum element
// in the second half
var maxSecond = Number.MIN_VALUE
// Calculate the maximum element
// int the second half
for (var i = mid; i < n; i++)
{
maxSecond = Math.max(maxSecond, arr[i]);
}
// Print the found maximums
document.write(maxFirst + ", " + maxSecond);
}
// Driver Code
var arr = [ 1, 12, 14, 5 ];
var n = arr.length;
findMax(arr, n);
// This code is contributed by bunnyram19.
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Time Complexity: O(n)
Auxiliary Space: O(1)
Python | Create two lists with first half and second half elements of a list
Here, we are going to learn how to create two lists with first half and second half elements of a given list in Python?
Submitted by IncludeHelp, on August 03, 2018
Given a list, and we have to create two lists from first half elements and second half elements of a list in Python.
Example:
Input: list: [10, 20, 30, 40, 50, 60] Output: list1: [10, 20, 30] list2: [40, 50, 60]Logic:
- First take list (Here, we are taking list with 6 elements).
- To get the elements from/till specified index, use list[n1:n2] notation.
- To get first half elements, we are using list[:3], it will return first 3 elements of the list.
- And, to get second half elements, we are using list[3:], it will return elements after first 3 elements. In this example, we have only 6 elements, so next 3 elements will be returned.
- Finally, print the lists.
Program:
# define a list list = [10, 20, 30, 40, 50, 60] # Create list1 with half elements (first 3 elements) list1 = list [:3] # Create list2 with next half elements (next 3 elements) list2 = list [3:] # print list (s) print "list : ",list print "list1: ",list1 print "list2: ",list2Output
list : [10, 20, 30, 40, 50, 60] list1: [10, 20, 30] list2: [40, 50, 60]Using list[0:3] and list[3:6] instaed of list[:3] and list[3:]
We can also use list[0:3] instead of list[:3] to get first 3 elements and list[3:6] instead of list[3:] to get next 3 elements after first 3 elements.
Consider the program:
# define a list list = [10, 20, 30, 40, 50, 60] # Create list1 with half elements (first 3 elements) list1 = list [0:3] # Create list2 with next half elements (next 3 elements) list2 = list [3:6] # print list (s) print "list : ",list print "list1: ",list1 print "list2: ",list2Output
list : [10, 20, 30, 40, 50, 60] list1: [10, 20, 30] list2: [40, 50, 60]By considering length of the list
Let suppose list has n elements, then we can use list[0:n/2] and list[n/2:n].
Consider the program:
If there are ODD numbers of elements in the list, program will display message "List has ODD number of elements." And exit.
# define a list list = [10, 20, 30, 40, 50, 60] # get the length of the list n = len(list) # condition to check length is EVEN or not # if lenght is ODD, show message and exit if( n%2 != 0 ): print "List has ODD number of elements." exit() # Create list1 with half elements (first 3 elements) list1 = list [0:n/2] # Create list2 with next half elements (next 3 elements) list2 = list [n/2:n] # print list (s) print "list : ",list print "list1: ",list1 print "list2: ",list2Output
list : [10, 20, 30, 40, 50, 60] list1: [10, 20, 30] list2: [40, 50, 60]Python List Programs »
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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
Find Maximum Value in a List in Python
Created: November-16, 2020 | Updated: December-10, 2020
This tutorial will demonstrate how to find the maximum value in a list in Python.
A few scenarios and data types will be covered, from a simple integer list to a more complex structure such as an array within an array.
Python program to find the second largest number in a list
In this article, we will learn about the solution to the problem statement given below.
Problem statement− We are given a list, we need to display the second largest number in a list.
There are three approaches to solve the problem−
Python Program to Create Two Lists with First Half and Second Half Elements of Given List
- Python program to create two lists with first half and second half elements of a given list.
- Python program to create two lists with first half and second half elements of a given list using range slicing.
1: Python program to create two lists with first half and second half elements of a given list
use the following steps to write a python program to create list in first half of the elements with the second half of the elements:
- Define a list.
- Take input how many element in list from user.
- Iterate for loop and use input() function to allow user to input element.
- Append elements in list by using append() method.
- Divide list length number by 2 and store in variable.
- To get first half elements usinglist[:num] and store list1.
- To get second half elements usinglist[num:] and store list2.
- Print list1 and list2.
After executing the program, the output will be:
How many elements in list :- 6 Please enter the Value of 1 Element :- 1 Please enter the Value of 2 Element :- 2 Please enter the Value of 3 Element :- 3 Please enter the Value of 4 Element :- 4 Please enter the Value of 5 Element :- 5 Please enter the Value of 6 Element :- 6 list : [1, 2, 3, 4, 5, 6] list1: [1, 2, 3] list2: [4, 5, 6]2: Python program to create two lists with first half and second half elements of a given list using range slicing
use the following steps to write a python program to create list in first half of the elements with the second half of the elements using range slicing:
After executing the program, the output will be:
How many elements in list :- 6 Please enter the Value of 1 Element :- 9 Please enter the Value of 2 Element :- 8 Please enter the Value of 3 Element :- 7 Please enter the Value of 4 Element :- 6 Please enter the Value of 5 Element :- 5 Please enter the Value of 6 Element :- 4 list : [9, 8, 7, 6, 5, 4] list1: [9, 8, 7] list2: [6, 5, 4]