Update topics

Author: jaychsu

topic/language/python/README.md

@@ -8,6 +8,25 @@ Python Syntax Note
 `is` will return True if two variables point to the same object,
 `==` if the objects referred to by the variables are equal.
 
+- example in `int` and `float`
+
+note that, negative `int`/`float` is special case.
+
+```python
+>>> 10 != 10
+False
+>>> 10 is not 10
+False
+>>> 0 != 0
+False
+>>> 0 is not 0
+False
+>>> -9 != -9
+False
+>>> -9 is not -9
+True
+```
+
 - example in `str` and `bytes`
 
 ```python

topic/linked_list/README.md

@@ -25,5 +25,5 @@ Linked List
 ```python
 >>> cur = None
 >>> while head:
-...     cur, cur.next, head = head, cur, head.next
+...     head.next, cur, head = cur, head, head.next
 ```

topic/problem_set/substring_with_distinct_characters.md

@@ -0,0 +1,16 @@
+- minimum length:
+
+    ```
+    while cnt == k:
+        # reduce window size if possible
+        # and record it
+    ```
+
+- maximum length:
+
+    ```
+    while cnt > k:
+        # to evict invalid start
+
+    # it's valid here, so record the maximum window size
+    ```