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Tested Python solution for LeetCode 650 with 14 pytest cases. Generate a practice environment with lcpy.
lcpy gen -n 650 # by problem number
lcpy gen -s two_keys_keyboard # by problem name
'A' on the screen of a notepad. You can perform one of two operations on this notepad for each step:
n, return the minimum number of operations to get the character 'A' exactly n times on the screen.
Input: n = 3
Output: 3
Explanation: Initially, we have one character 'A'.
In step 1, we use Copy All operation.
In step 2, we use Paste operation to get 'AA'.
In step 3, we use Paste operation to get 'AAA'.
Input: n = 1
Output: 0
class Solution:
# Time: O(sqrt(n))
# Space: O(1)
def min_steps(self, n: int) -> int:
# Each run of pastes multiplies the screen by a factor; copying a
# block of size d costs d operations total, so the answer is the sum
# of the prime factors of n.
operations = 0
factor = 2
while factor * factor <= n:
while n % factor == 0:
operations += factor
n //= factor
factor += 1
if n > 1:
operations += n
return operations
| Time | Space |
|---|---|
| O(sqrt(n)) | O(1) |