------
## 最终结论
```python
def smallestRangeI(A, K):
    max_A = max(A)
    min_A = min(A)
    
    # Calculate the initial difference
    initial_difference = max_A - min_A
    
    # Adjust the maximum and minimum values
    new_max = max_A - K
    new_min = min_A + K
    
    # Calculate the new difference
    new_difference = new_max - new_min
    
    # Return the smallest difference, ensuring it is not negative
    return max(0, new_difference)

# Example usage:
A1 = [1]
K1 = 0
print(smallestRangeI(A1, K1))  # Output: 0

A2 = [0, 10]
K2 = 2
print(smallestRangeI(A2, K2))  # Output: 6

A3 = [1, 3, 6]
K3 = 3
print(smallestRangeI(A3, K3))  # Output: 3
```