Question

How to find an element that appears once in a list of elements that appears three times in Python

Answer 1

from collections import defaultdict

def FindElementThatAppearsOnceInArray(lst):
    # initialize a dictionary that will assign a  
    # default value to non-existent keys
    dict = defaultdict(int)

    for x in lst:
        dict[x] += 1

    for x, freq in dict.items():
        if freq == 1:
            return x
    
    return -1
    

lst = [3, 5, 5, 2, 7, 3, 2, 8, 8, 3, 2, 5, 8]

print(FindElementThatAppearsOnceInArray(lst))



'''
run:

7

'''

 

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