Given a positive integer n
, you can apply one of the following operations:
- If
n
is even, replacen
withn / 2
. - If
n
is odd, replacen
with eithern + 1
orn - 1
.
Return the minimum number of operations needed for n
to become 1
.
Example 1:
Input: n = 8
Output: 3
Explanation: 8 -> 4 -> 2 -> 1
Example 2:
Input: n = 7
Output: 4
Explanation: 7 -> 8 -> 4 -> 2 -> 1
or 7 -> 6 -> 3 -> 2 -> 1
Example 3:
Input: n = 4
Output: 2
Constraints:
-
1 <= n <= 231 - 1
SOLUTION:
class Solution:
def integerReplacement(self, n: int) -> int:
if n == 1:
return 0
if n == 3:
return 2
if n & 1:
if (n + 1) & 3 == 0:
return 3 + self.integerReplacement((n + 1) >> 2)
else:
return 2 + self.integerReplacement((n - 1) >> 1)
else:
return 1 + self.integerReplacement(n >> 1)
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