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Python | Program to print duplicates from a list of integers

  • Difficulty Level : Easy
  • Last Updated : 31 May, 2021

Given a list of integers with duplicate elements in it. The task to generate another list, which contains only the duplicate elements. In simple words, the new list should contain the elements which appear more than one.
 

Examples : 

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Input : list = [10, 20, 30, 20, 20, 30, 40, 50, -20, 60, 60, -20, -20]
Output : output_list = [20, 30, -20, 60]


Input :  list = [-1, 1, -1, 8]
Output : output_list = [-1]

Method 1: Using the Brute Force approach



Below is the implementation : 

Python3




# Python program to print
# duplicates from a list
# of integers
def Repeat(x):
    _size = len(x)
    repeated = []
    for i in range(_size):
        k = i + 1
        for j in range(k, _size):
            if x[i] == x[j] and x[i] not in repeated:
                repeated.append(x[i])
    return repeated
 
# Driver Code
list1 = [10, 20, 30, 20, 20, 30, 40,
         50, -20, 60, 60, -20, -20]
print (Repeat(list1))
     
# This code is contributed
# by Sandeep_anand

Output : 

[20, 30, -20, 60]

Method 2: Using Counter() function from collection module

Python3




from collections import Counter
 
l1 = [1,2,1,2,3,4,5,1,1,2,5,6,7,8,9,9]
d = Counter(l1)
print(d)
 
new_list = list([item for item in d if d[item]>1])
print(new_list)
Output
Counter({1: 4, 2: 3, 5: 2, 9: 2, 3: 1, 4: 1, 6: 1, 7: 1, 8: 1})
[1, 2, 5, 9]



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