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Update climbing_stairs.py

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marina 2023-08-07 16:55:25 -07:00 committed by GitHub
parent bce645eb9e
commit 784b8a8698
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1 changed files with 13 additions and 15 deletions
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dynamic_programming/climbing_stairs.py
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@ -10,38 +10,42 @@ In how many distinct ways can you climb to the top?
def climb_stairs_o2n(n: int) -> int: def climb_stairs_o2n(n: int) -> int:
if n == 0 or n == 1: if n == 0 or n == 1:
return 1 return 1
return climb_stairs_o2n(n-1) + climb_stairs_o2n(n-2) return climb_stairs_o2n(n-1) + climb_stairs_o2n(n-2)
def climb_stairs_memoization(n: int) -> int:
def helper(n: int, memo: dict[int, int]) -> int: memo = {}
def helper(n: int, memo: dict[int, int]) -> int:
if n == 0 or n == 1: if n == 0 or n == 1:
return 1 return 1
if n not in memo: if n not in memo:
memo[n] = helper(n-1, memo) + helper(n-2, memo) memo[n] = helper(n-1, memo) + helper(n-2, memo)
return memo[n] return memo[n]
def climb_stairs_memoization(n: int) -> int:
memo = {}
return helper(n, memo) return helper(n, memo)
def climb_stairs_optimized(n: int) -> int: def climb_stairs_optimized(n: int) -> int:
if n == 0 or n == 1: if n == 0 or n == 1:
return 1 return 1
prev, curr = 1, 1 prev, curr = 1, 1
for i in range(2, n+1): for i in range(2, n+1):
temp = curr temp = curr
curr = prev + curr curr = prev + curr
prev = temp prev = temp
return curr return curr
def climb_stairs_tabulation(n: int) -> int: def climb_stairs_tabulation(n: int) -> int:
if n == 0 or n == 1: if n == 0 or n == 1:
return 1 return 1
@ -50,11 +54,5 @@ def climb_stairs_tabulation(n: int) -> int:
for i in range(2, n+1): for i in range(2, n+1):
dp[i] = dp[i-1] + dp[i-2] dp[i] = dp[i-1] + dp[i-2]
return dp[n] return dp[n]
if __name__ == "__main__":
print(climb_stairs_o2n(4))
print(climb_stairs_memoization(4))
print(climb_stairs_optimized(4))
print(climb_stairs_tabulation(4))