declass

Author: andrewlihk

Fibonacci Number - Leetcode 509/Fibonacci Number - Leetcode 509.py

@@ -2,70 +2,72 @@
 
 # Time: O(2^n)
 # Space: O(n)
-class Solution:
-    def fib(self, n: int) -> int:
-        if n == 0:
-            return 0
-        elif n == 1:
-            return 1
-        else:
-            return self.fib(n-1) + self.fib(n-2)
+
+def fib(n: int) -> int:
+    if n == 0:
+        return 0
+    elif n == 1:
+        return 1
+    else:
+        return fib(n-1) + fib(n-2)
 
 
 # Top Down Memoized
 
 # Time: O(n)
 # Space: O(n)
-class Solution:
-    def fib(self, n: int) -> int:
-        memo = {0:0, 1:1}
 
-        def f(x):
-            if x in memo:
-                return memo[x]
-            else:
-                memo[x] = f(x-1) + f(x-2)
-                return memo[x]
-        
-        return f(n)
+def fib2(n: int) -> int:
+    memo = {0:0, 1:1}
+
+    def f(x):
+        if x in memo:
+            return memo[x]
+        else:
+            memo[x] = f(x-1) + f(x-2)
+            return memo[x]
+    
+    return f(n)
 
 
 # Bottom Up Tabulation
 
 # Time: O(n)
 # Space: O(n)
-class Solution:
-    def fib(self, n: int) -> int:
-        if n == 0:
-            return 0
-        if n == 1:
-            return 1
 
-        dp = [0] * (n+1)
-        dp[0] = 0
-        dp[1] = 1
+def fib3(n: int) -> int:
+    if n == 0:
+        return 0
+    if n == 1:
+        return 1
+
+    dp = [0] * (n+1)
+    dp[0] = 0
+    dp[1] = 1
 
-        for i in range(2, n+1):
-            dp[i] = dp[i-2] + dp[i-1]
+    for i in range(2, n+1):
+        dp[i] = dp[i-2] + dp[i-1]
 
-        return dp[n]
+    return dp[n]
 
 
 # Bottom Up Constant Space
 
 # Time: O(n)
 # Space: O(1)
-class Solution:
-    def fib(self, n: int) -> int:
-        if n == 0:
-            return 0
-        if n == 1:
-            return 1
-
-        prev = 0
-        cur = 1
-
-        for i in range(2, n+1):
-            prev, cur = cur, prev+cur
-        
-        return cur
+
+def fib4(n: int) -> int:
+    if n == 0:
+        return 0
+    if n == 1:
+        return 1
+
+    prev = 0
+    cur = 1
+
+    for i in range(2, n+1):
+        prev, cur = cur, prev+cur
+    
+    return cur
+
+print(fib4(10))