Find All Duplicates in an Array

Question

Given an array of integers, find all the duplicates in the array and return them in an array.

Example 1

Input: [4,3,2,7,8,2,3,1]

Output: [2,3]

Solution

▭

all//Find All Duplicates in an Array.py

def find_duplicates(arr):
    duplicates = []

    for i in range(len(arr)):
        if arr[abs(arr[i])] >= 0:
            arr[abs(arr[i])] = -arr[abs(arr[i])]
        else:
            duplicates.append(abs(arr[i]))

    return duplicates

arr = [1,2,3,2,4,5,3]
print(find_duplicates(arr)) # Output: [2,3]

▯

all//Find All Duplicates in an Array.py

def find_duplicates(arr):
    duplicates = []

    for i in range(len(arr)):
        if arr[abs(arr[i])] >= 0:
            arr[abs(arr[i])] = -arr[abs(arr[i])]
        else:
            duplicates.append(abs(arr[i]))

    return duplicates

arr = [1,2,3,2,4,5,3]
print(find_duplicates(arr)) # Output: [2,3]