Calculate the Sum of Cubes of a Range
Quick Overview
`sum(n**3 for n in range(x))` streams one value at a time, where the bracketed comprehension materialises every cube first. Same answer, `O(1)` memory against `O(n)`.
Deep Dive
1. The Challenge: Summing Cubed Values
Create a function sum_of_cubes(nums) that takes a list of numbers and returns the sum of its cubes (n^3).
2. Why It Matters
Generator expressions paired with sum() enable performing mathematical transformations across datasets without allocating intermediate lists in memory.
3. The Python Solution
Use Python's built-in sum() with a generator expression x**3:
def sum_of_cubes(nums):
return sum(x**3 for x in nums)
# Testing our function
print(sum_of_cubes([1, 5, 9])) # Output: 855 (1 + 125 + 729)
print(sum_of_cubes([3, 4, 5])) # Output: 216 (27 + 64 + 125)
print(sum_of_cubes([2])) # Output: 8
print(sum_of_cubes([])) # Output: 0
4. Exponentiation Operator (**)
In Python, x**3 raises x to the power of 3 (do NOT use x ^ 3, as ^ is Python's bitwise XOR operator!).
5. Common Mistakes
- Bitwise XOR Mistake: Writing
x ^ 3performs bitwise XOR logic, NOT exponentiation! Always use double asterisksx ** 3orpow(x, 3)for powers in Python.
6. Next Steps
Use ** for exponents and sum() for aggregations. Next, let's check for symmetrical numbers and palindromes!
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