 # Python Program to Find the Sum of all Even Occurring Elements in an Array/List

In the previous article, we have discussed Python Program to Find the sum of all Highest Occurring Elements in an Array/List

Given a list, the task is to find the sum of the elements which are having an even frequency in the given array/List.

Examples:

Example1:

Input:

Given List = [6, 1, 4, 1, 1, 6, 4, 4, 2, 2]

Output:

The sum of all even frequency elements in the given list [6, 1, 4, 1, 1, 6, 4, 4, 2, 2] is:
8

Explanation:

Here 6,2 are the elements in the given list which are having even frequency
sum=6+2=8

Example2:

Input:

Given List = [7, 6, 8, 8, 1, 4, 1, 5, 4, 7]

Output:

The sum of all even frequency elements in the given list [7, 6, 8, 8, 1, 4, 1, 5, 4, 7] is:
20

## Program to Find the Sum of all Even Occurring Elements in an Array/List in Python

Below are the ways to find the sum of the elements which are having an even frequency in the given array/List:

### Method #1: Using Dictionary (Hashing, Static Input)

Approach:

• Take a dictionary and initialize it to empty using the {} or dict() say freqncyDictionary.
• Give the list as static input and store it in a variable.
• Loop in the given list using the For loop.
• Inside the For loop, Check if the list element is present in the dictionary or not using the if conditional statement and ‘in‘ keyword.
• If it is true then increment the count of the list element in the dictionary by 1.
• Else initialize the dictionary with the list element as key and value as 1.
• Take a variable say evenfreqncycnt and initialize its value to 0.
• Loop in the freqncyDictionary using the For loop.
• Check if the key in the freqncyDictionary having value even using the if conditional statement.
• If it is true then increment the evenfreqncycnt by the key and store it in the same variable.
• After the end of For loop then print the evenfreqncycnt value.
• The Exit of the Program.

Below is the implementation:

# Take a dictionary and initialize it to empty
# using the {} or dict() say freqncyDictionary.
freqncyDictionary = {}
# Give the list as static input and store it in a variable.
gvnlst = [6, 1, 4, 1, 1, 6, 4, 4, 2, 2]
# Loop in the given list using the For loop.
for i in gvnlst:
# Inside the For loop,
# Check if the list element is present in the dictionary
# or not using the if conditional statement and 'in' keyword.
if i in freqncyDictionary.keys():
# If it is true then increment the count of the list element
# in the dictionary by 1.
freqncyDictionary[i] = freqncyDictionary[i]+1
# Else initialize the dictionary with the list element as key and value as 1.
else:
freqncyDictionary[i] = 1

# Take a variable say evenfreqncycnt and initialize its value to 0.
evenfreqncycnt = 0
# Loop in the freqncyDictionary using the For loop.
for elemnt in freqncyDictionary:
# Check if the key in the freqncyDictionary having value even
# using the if conditional statement.
if(freqncyDictionary[elemnt] % 2 == 0):
# If it is true then increment the evenfreqncycnt by the key
# and store it in the same variable.
evenfreqncycnt += elemnt
# After the end of For loop then print the evenfreqncycnt value.
print('The sum of all even frequency elements in the given list', gvnlst, 'is:')
print(evenfreqncycnt)


Output:

The sum of all even frequency elements in the given list [6, 1, 4, 1, 1, 6, 4, 4, 2, 2] is:
8

### Method #2: Using Dictionary (Hashing, User Input)

Approach:

• Take a dictionary and initialize it to empty using the {} or dict() say freqncyDictionary.
• Give the list as user input using the list(),map(),split(),int functions and store it in a variable.
• Loop in the given list using the For loop.
• Inside the For loop, Check if the list element is present in the dictionary or not using the if conditional statement and ‘in‘ keyword.
• If it is true then increment the count of the list element in the dictionary by 1.
• Else initialize the dictionary with the list element as key and value as 1.
• Take a variable say evenfreqncycnt and initialize its value to 0.
• Loop in the freqncyDictionary using the For loop.
• Check if the key in the freqncyDictionary having value even using the if conditional statement.
• If it is true then increment the evenfreqncycnt by the key and store it in the same variable.
• After the end of For loop then print the evenfreqncycnt value.
• The Exit of the Program.

Below is the implementation:

# Take a dictionary and initialize it to empty
# using the {} or dict() say freqncyDictionary.
freqncyDictionary = {}
# Give the list as user input using the list(),map(),split(),int functions
# and store it in a variable.
gvnlst = list(
map(int, input('Enter some random list element separated by spaces = ').split()))
# Loop in the given list using the For loop.
for i in gvnlst:
# Inside the For loop,
# Check if the list element is present in the dictionary
# or not using the if conditional statement and 'in' keyword.
if i in freqncyDictionary.keys():
# If it is true then increment the count of the list element
# in the dictionary by 1.
freqncyDictionary[i] = freqncyDictionary[i]+1
# Else initialize the dictionary with the list element as key and value as 1.
else:
freqncyDictionary[i] = 1

# Take a variable say evenfreqncycnt and initialize its value to 0.
evenfreqncycnt = 0
# Loop in the freqncyDictionary using the For loop.
for elemnt in freqncyDictionary:
# Check if the key in the freqncyDictionary having value even
# using the if conditional statement.
if(freqncyDictionary[elemnt] % 2 == 0):
# If it is true then increment the evenfreqncycnt by the key
# and store it in the same variable.
evenfreqncycnt += elemnt
# After the end of For loop then print the evenfreqncycnt value.
print('The sum of all even frequency elements in the given list', gvnlst, 'is:')
print(evenfreqncycnt)


Output:

Enter some random list element separated by spaces = 1 2 3 4 5 1 3 4
The sum of all even frequency elements in the given list [1, 2, 3, 4, 5, 1, 3, 4] is:
8

### Method #3: Using Counter() function (Hashing, Static Input)

Approach:

• Import the Counter() function from collections using the import keyword.
• Give the list as static input and store it in a variable.
• Calculate the frequency of all the given list elements using the Counter() function which returns the element and its frequency as key-value pair and store this dictionary in a variable(say freqncyDictionary)
• Take a variable say evenfreqncycnt and initialize its value to 0.
• Loop in the freqncyDictionary using the For loop.
• Check if the key in the freqncyDictionary having value even using the if conditional statement.
• If it is true then increment the evenfreqncycnt by the key and store it in the same variable.
• After the end of For loop then print the evenfreqncycnt value.
• The Exit of the Program.

Below is the implementation:

# Import the Counter() function from collections using the import keyword.
from collections import Counter
# Give the list as static input and store it in a variable.
gvnlst = [10, 4, 2, 10, 1, 2, 3, 4, 5, 6, 6]
# Calculate the frequency of all the given list elements using the Counter()
# function which returns the element and its frequency as key-value pair
# and store this dictionary in a variable(say freqncyDictionary)
freqncyDictionary = Counter(gvnlst)

# Take a variable say evenfreqncycnt and initialize its value to 0.
evenfreqncycnt = 0
# Loop in the freqncyDictionary using the For loop.
for elemnt in freqncyDictionary:
# Check if the key in the freqncyDictionary having value even
# using the if conditional statement.
if(freqncyDictionary[elemnt] % 2 == 0):
# If it is true then increment the evenfreqncycnt by the key
# and store it in the same variable.
evenfreqncycnt += elemnt
# After the end of For loop then print the evenfreqncycnt value.
print('The sum of all even frequency elements in the given list', gvnlst, 'is:')
print(evenfreqncycnt)


Output:

The sum of all even frequency elements in the given list [10, 4, 2, 10, 1, 2, 3, 4, 5, 6, 6] is:
22

### Method #4: Using Counter() function (Hashing, User Input)

Approach:

• Import the Counter() function from collections using the import keyword.
• Give the list as user input using the list(),map(),split(),int functions and store it in a variable.
• Calculate the frequency of all the given list elements using the Counter() function which returns the element and its frequency as key-value pair and store this dictionary in a variable(say freqncyDictionary)
• Take a variable say evenfreqncycnt and initialize its value to 0.
• Loop in the freqncyDictionary using the For loop.
• Check if the key in the freqncyDictionary having value even using the if conditional statement.
• If it is true then increment the evenfreqncycnt by the key and store it in the same variable.
• After the end of For loop then print the evenfreqncycnt value.
• The Exit of the Program.

Below is the implementation:

# Import the Counter() function from collections using the import keyword.
from collections import Counter
# Give the list as user input using the list(),map(),split(),int functions
# and store it in a variable.
gvnlst = list(
map(int, input('Enter some random list element separated by spaces = ').split()))
# Calculate the frequency of all the given list elements using the Counter()
# function which returns the element and its frequency as key-value pair
# and store this dictionary in a variable(say freqncyDictionary)
freqncyDictionary = Counter(gvnlst)

# Take a variable say evenfreqncycnt and initialize its value to 0.
evenfreqncycnt = 0
# Loop in the freqncyDictionary using the For loop.
for elemnt in freqncyDictionary:
# Check if the key in the freqncyDictionary having value even
# using the if conditional statement.
if(freqncyDictionary[elemnt] % 2 == 0):
# If it is true then increment the evenfreqncycnt by the key
# and store it in the same variable.
evenfreqncycnt += elemnt
# After the end of For loop then print the evenfreqncycnt value.
print('The sum of all even frequency elements in the given list', gvnlst, 'is:')
print(evenfreqncycnt)


Output:

Enter some random list element separated by spaces = 3 4 1 2 4 1 3
The sum of all even frequency elements in the given list [3, 4, 1, 2, 4, 1, 3] is:
8

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