﻿ Python: Find the first duplicate element in a given array of integers - w3resource # Python: Find the first duplicate element in a given array of integers

## Python: Array Exercise-15 with Solution

Write a Python program to find the first duplicate element in a given array of integers. Return -1 If there are no such elements.

Sample Solution:

Python Code :

``````def find_first_duplicate(nums):
num_set = set()
no_duplicate = -1

for i in range(len(nums)):

if nums[i] in num_set:
return nums[i]
else:

return no_duplicate

print(find_first_duplicate([1, 2, 3, 4, 4, 5]))
print(find_first_duplicate([1, 2, 3, 4]))
print(find_first_duplicate([1, 1, 2, 3, 3, 2, 2]))
``````

Sample Output:

```4
-1
1
```

Python Code Editor:

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## Python: Tips of the Day

Python: Membership Testing in a Collection

```>>> a = ('one', 'two', 'three', 'four', 'five')
>>> if 'one' in a:
...     print('The tuple contains one.')
...
The tuple contains one.
>>> b = {0: 'zero', 1: 'one', 2: 'two', 3: 'three'}
>>> if 2 in b.keys():
...     print('The dict has the key of 2.')
...
The dict has the key of 2.
```