first commit

p14/solution.py

@@ -0,0 +1,34 @@
+def solution(n):
+    n_steps = {}
+    i = 1
+    number = 1
+    chain = [1]
+    result = (i, len(chain))
+    while i < n:
+        if number == 1:
+            chain_length = len(chain)
+            for j in range(chain_length-1):
+                n_steps[chain[j]] = chain_length - j
+            if chain_length > result[1]:
+                result = (i, chain_length)
+            i += 1
+            number = i
+            chain = [i]
+        if number in n_steps:
+            chain_length = len(chain) + n_steps[number] - 1
+            for j in range(len(chain)-1):
+                n_steps[chain[j]] = chain_length - j
+            if chain_length > result[1]:
+                result = (i, chain_length)
+            i += 1
+            number = i
+            chain = [i]
+        elif number % 2 == 0:
+            number //= 2
+            chain.append(number)
+        else:
+            number = 3*number +1
+            chain.append(number)
+    return result
+
+print(solution(1000000))