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Algorithms & data structures

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Algorithms & data structures easy

Find First Duplicate Index in Python

Return the index of the first element that appears more than once in a list, using a dictionary for O(n) time.

duplicate dictionary arrays
Python 
def find_first_duplicate(arr):
    seen = {}
    for index, value in enumerate(arr):
        if value in seen:
            return index
        seen[value] = index
    return -1

if __name__ == "__main__":
    test_array = [3, 5, 2, 8, 5, 1, 2]
    result = find_first_duplicate(test_array)
    print(f"Array: {test_arr…
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