leetcode-solution/Python/0070-climbing-stairs.py at main · hogan-tech/leetcode-solution · GitHub

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
from functools import lru_cache


# time complexity: O(n)
# space complexity: O(n)
# Cashe with brute force
class Solution:
    def climbStairs(self, n: int) -> int:
        memo = [0] * (n+1)
        return self.climb_Stairs(0, n, memo)

# time complexity: O(n)
# space complexity: O(n)
class Solution:
    def climb_Stairs(self, i: int, n: int, memo: list) -> int:
        if (i > n):
            return 0
        if (i == n):
            return 1
        if (memo[i]):
            return memo[i]
        memo[i] = self.climb_Stairs(i+1, n, memo) + \
            self.climb_Stairs(i+2, n, memo)
        return memo[i]

# time complexity: O(n)
# space complexity: O(b)
# Dynamic Programming
class Solution:
    def climbStairs(self, n: int):
        if n == 1:
            return 1
        dp = [0] * (n + 1)
        dp[1] = 1
        dp[2] = 2
        for i in range(3, n+1):
            dp[i] = dp[i-1] + dp[i-2]
        return dp[n]

# time complexity: O(n)
# space complexity: O(1)
# Fibonacci Number
class Solution:
    def climbStairs(self, n: int) -> int:
        if n == 1:
            return 1
        first = 1
        second = 2
        third = 0
        for i in range(3, n+1):
            third = first + second
            first = second
            second = third
        return second

class Solution:
    @lru_cache(None)
    def climbStairs(self, n: int) -> int:
        if n == 1:
            return 1
        if n == 2:
            return 2
        return self.climbStairs(n-1) + self.climbStairs(n-2)


n = 50
print(Solution().climbStairs(50))