------
## 最终结论
```python
def test_duplicate(arr):
    return len(arr) != len(set(arr))

# Test cases
assert test_duplicate([1, 2, 3, 4, 5]) == False
assert test_duplicate([1, 2, 3, 4, 4]) == True
assert test_duplicate([1, 1, 2, 2, 3, 3, 4, 4, 5]) == True
```