optimize code structure

Leetcode/tools.py

@@ -0,0 +1,11 @@
+import time
+
+
+def timer(func):
+    def wrapper(s):
+        start_time = time.time()
+        str_len = func(s)
+        end_time = time.time()
+        print(f"func name: {func.__name__}, total cost: {round((end_time - start_time) * 1000 * 1000, 2)} ns")
+        return str_len
+    return wrapper