Update Solution.py

solution/0800-0899/0818.Race Car/Solution.py

@@ -1,12 +1,9 @@
 class Solution:
-    def racecar(self, target: int) -> int:
-        dp = [0] * (target + 1)
-        for i in range(1, target + 1):
-            k = i.bit_length()
-            if i == 2**k - 1:
-                dp[i] = k
-                continue
-            dp[i] = dp[2**k - 1 - i] + k + 1
-            for j in range(k - 1):
-                dp[i] = min(dp[i], dp[i - (2 ** (k - 1) - 2**j)] + k - 1 + j + 2)
-        return dp[target]
+    def pruneTree(self, root):
+        if not root:
+            return None
+        root.left = self.pruneTree(root.left)
+        root.right = self.pruneTree(root.right)
+        if not root.left and not root.right and root.val == 0:
+            return None
+        return root