forked from shuboc/LeetCode-2
-
Notifications
You must be signed in to change notification settings - Fork 0
/
integer-replacement.py
73 lines (67 loc) · 1.38 KB
/
integer-replacement.py
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
# Time: O(logn)
# Space: O(1)
# Given a positive integer n and you can do operations as follow:
#
# If n is even, replace n with n/2.
# If n is odd, you can replace n with either n + 1 or n - 1.
# What is the minimum number of replacements needed for n to become 1?
#
# Example 1:
#
# Input:
# 8
#
# Output:
# 3
#
# Explanation:
# 8 -> 4 -> 2 -> 1
# Example 2:
#
# Input:
# 7
#
# Output:
# 4
#
# Explanation:
# 7 -> 8 -> 4 -> 2 -> 1
# or
# 7 -> 6 -> 3 -> 2 -> 1
# Iterative solution.
class Solution(object):
def integerReplacement(self, n):
"""
:type n: int
:rtype: int
"""
result = 0
while n != 1:
b = n & 3
if n == 3:
n -= 1
elif b == 3:
n += 1
elif b == 1:
n -= 1
else:
n /= 2
result += 1
return result
# Time: O(logn)
# Space: O(logn)
# Recursive solution.
class Solution2(object):
def integerReplacement(self, n):
"""
:type n: int
:rtype: int
"""
if n < 4:
return [0, 0, 1, 2][n]
if n % 4 in (0, 2):
return self.integerReplacement(n / 2) + 1
elif n % 4 == 1:
return self.integerReplacement((n - 1) / 4) + 3
else:
return self.integerReplacement((n + 1) / 4) + 3