climbing stairs

Author: bskkimm

climbing-stairs/bskkimm.py

@@ -0,0 +1,23 @@
+class Solution:
+    def __init__(self):
+        self.memo = {}
+    
+    def climbStairs(self, n: int) -> int:
+        
+        # n = 3 --> 3: 111, 2: 12, 21: --> 3
+        # n = 4 --> 4: 1111, 3: 112, 121, 211, 2: 22 --> 5
+        # n = 5 --< 5: 11111,4: 1112, 1121, 1211, 2111, 3: 221, 212, 122, --> 8
+        # n = 6 --> 6: 111111, 5: 5, 4: 2211, 1122, 1221, 2112, 1212, 2121, 3: 1 --> 13
+
+        # a(n+2) = a(n+1) + a(n)
+
+        if n == 1:
+            return 1
+        elif n == 2:
+            return 2
+
+        if n in self.memo: # need to return when memo is available w.r.t n
+            return self.memo[n]
+
+        self.memo[n] = self.climbStairs(n-1) + self.climbStairs(n-2)
+        return self.memo[n]