First missing positive number

Examples

1. first_missing_positive([-3, 4, 1]) should return 2.
2. first_missing_positive([0, 2, 1, 4]) should return 3.
3. first_missing_positive([-5, 1, -2, 2, 3]) should return 4.
4. first_missing_positive([2, 1, 3, 4]) should return 5.

Try it first

1def first_missing_positive(arr: list[int]) -> int:
2    # implement first_missing_positive here
3    return 0
4

Solution