godelian · godelian · Oct 9, 2019 · May 12, 2017 · May 16, 2017 · May 16, 2017
diff --git a/.gitignore b/.gitignore
@@ -1,4 +1,5 @@
 # Byte-compiled / optimized / DLL files
+*.epub
 __pycache__/
 *.py[cod]
 

diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
@@ -65,6 +65,7 @@ Translations to new languages are always welcome, especially if you can maintain
 * Invite friends to review if possible. If desired, feel free to invite friends to help your original translation by letting them fork your repo, then merging their PRs.
 * Add links to your translation at the top of every README*.md file. (For consistency, the link should be added in alphabetical order by ISO code, and the anchor text should be in the native language.)
 * When done, indicate on the PR that it's ready to be merged into the main repo.
+* Once accepted, your PR will be squashed into a single commit into the `master` branch.
 
 ### Translation template credits
 

diff --git a/LICENSE.txt b/LICENSE.txt
@@ -1,3 +1,9 @@
+I am providing code and resources in this repository to you under an open source
+license.  Because this is my personal repository, the license you receive to my
+code and resources is from me and not my employer (Facebook).
+
+Copyright 2017 Donne Martin
+
 Creative Commons Attribution 4.0 International License (CC BY 4.0)
 
 http://creativecommons.org/licenses/by/4.0/
diff --git a/README-ja.md b/README-ja.md
diff --git a/README-zh-Hans.md b/README-zh-Hans.md
diff --git a/README-zh-TW.md b/README-zh-TW.md
diff --git a/README.md b/README.md
diff --git a/epub-metadata.yaml b/epub-metadata.yaml
@@ -0,0 +1,3 @@
+title: System Design Primer
+creator: Donne Martin
+date: 2018
diff --git a/generate-epub.sh b/generate-epub.sh
@@ -0,0 +1,40 @@
+#! /usr/bin/env sh
+
+generate_from_stdin() {
+  outfile=$1
+  language=$2
+
+  echo "Generating '$language' ..."
+
+  pandoc --metadata-file=epub-metadata.yaml --metadata=lang:$2 --from=markdown -o $1 <&0
+
+  echo "Done! You can find the '$language' book at ./$outfile"
+}
+
+generate_with_solutions () {
+  tmpfile=$(mktemp /tmp/sytem-design-primer-epub-generator.XXX)
+
+  cat ./README.md >> $tmpfile
+
+  for dir in ./solutions/system_design/*; do 
+    case $dir in *template*) continue;; esac
+    case $dir in *__init__.py*) continue;; esac
+    : [[ -d "$dir" ]] && ( cd "$dir" && cat ./README.md >> $tmpfile && echo "" >> $tmpfile )
+  done
+
+  cat $tmpfile | generate_from_stdin 'README.epub' 'en'
+
+  rm "$tmpfile"
+}
+
+generate () {
+  name=$1
+  language=$2
+
+  cat $name.md | generate_from_stdin $name.epub $language
+}
+
+generate_with_solutions
+generate README-ja ja
+generate README-zh-Hans zh-Hans
+generate README-zh-TW zh-TW
diff --git a/solutions/object_oriented_design/call_center/call_center.ipynb b/solutions/object_oriented_design/call_center/call_center.ipynb
@@ -4,7 +4,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "This notebook was prepared by [Donne Martin](https://github.com/donnemartin). Source and license info is on [GitHub](https://github.com/donnemartin/system-design-primer-primer)."
+    "This notebook was prepared by [Donne Martin](https://github.com/donnemartin). Source and license info is on [GitHub](https://github.com/donnemartin/system-design-primer)."
    ]
   },
   {
@@ -24,9 +24,9 @@
     "    * Operator, supervisor, director\n",
     "* Can we assume operators always get the initial calls?\n",
     "    * Yes\n",
-    "* If there is no free operators or the operator can't handle the call, does the call go to the supervisors?\n",
+    "* If there is no available operators or the operator can't handle the call, does the call go to the supervisors?\n",
     "    * Yes\n",
-    "* If there is no free supervisors or the supervisor can't handle the call, does the call go to the directors?\n",
+    "* If there is no available supervisors or the supervisor can't handle the call, does the call go to the directors?\n",
     "    * Yes\n",
     "* Can we assume the directors can handle all calls?\n",
     "    * Yes\n",

diff --git a/solutions/object_oriented_design/call_center/call_center.py b/solutions/object_oriented_design/call_center/call_center.py
@@ -112,6 +112,11 @@ def _dispatch_call(self, call, employees):
                 return employee
         return None
 
-    def notify_call_escalated(self, call):  # ...
-    def notify_call_completed(self, call):  # ...
-    def dispatch_queued_call_to_newly_freed_employee(self, call, employee):  # ...
+    def notify_call_escalated(self, call):
+        pass
+
+    def notify_call_completed(self, call):
+        pass
+
+    def dispatch_queued_call_to_newly_freed_employee(self, call, employee):
+        pass
diff --git a/solutions/object_oriented_design/deck_of_cards/deck_of_cards.ipynb b/solutions/object_oriented_design/deck_of_cards/deck_of_cards.ipynb
@@ -4,7 +4,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "This notebook was prepared by [Donne Martin](https://github.com/donnemartin). Source and license info is on [GitHub](https://github.com/donnemartin/system-design-primer-primer)."
+    "This notebook was prepared by [Donne Martin](https://github.com/donnemartin). Source and license info is on [GitHub](https://github.com/donnemartin/system-design-primer)."
    ]
   },
   {
@@ -89,11 +89,11 @@
     "        super(BlackJackCard, self).__init__(value, suit)\n",
     "\n",
     "    def is_ace(self):\n",
-    "        return True if self._value == 1 else False\n",
+    "        return self._value == 1\n",
     "\n",
     "    def is_face_card(self):\n",
     "        \"\"\"Jack = 11, Queen = 12, King = 13\"\"\"\n",
-    "        return True if 10 < self._value <= 13 else False\n",
+    "        return 10 < self._value <= 13\n",
     "\n",
     "    @property\n",
     "    def value(self):\n",

diff --git a/solutions/object_oriented_design/deck_of_cards/deck_of_cards.py b/solutions/object_oriented_design/deck_of_cards/deck_of_cards.py
@@ -68,7 +68,7 @@ def add_card(self, card):
 
     def score(self):
         total_value = 0
-        for card in card:
+        for card in self.cards:
             total_value += card.value
         return total_value
 
@@ -92,7 +92,7 @@ def score(self):
 
     def possible_scores(self):
         """Return a list of possible scores, taking Aces into account."""
-        # ...
+        pass
 
 
 class Deck(object):
@@ -102,9 +102,9 @@ def __init__(self, cards):
         self.deal_index = 0
 
     def remaining_cards(self):
-        return len(self.cards) - deal_index
+        return len(self.cards) - self.deal_index
 
-    def deal_card():
+    def deal_card(self):
         try:
             card = self.cards[self.deal_index]
             card.is_available = False
@@ -113,4 +113,5 @@ def deal_card():
             return None
         return card
 
-    def shuffle(self):  # ...
+    def shuffle(self):
+        pass
diff --git a/solutions/object_oriented_design/hash_table/hash_map.ipynb b/solutions/object_oriented_design/hash_table/hash_map.ipynb
@@ -4,7 +4,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "This notebook was prepared by [Donne Martin](https://github.com/donnemartin). Source and license info is on [GitHub](https://github.com/donnemartin/system-design-primer-primer)."
+    "This notebook was prepared by [Donne Martin](https://github.com/donnemartin). Source and license info is on [GitHub](https://github.com/donnemartin/system-design-primer)."
    ]
   },
   {

diff --git a/solutions/object_oriented_design/hash_table/hash_map.py b/solutions/object_oriented_design/hash_table/hash_map.py
@@ -35,4 +35,4 @@ def remove(self, key):
             if item.key == key:
                 del self.table[hash_index][index]
                 return
-        raise KeyError('Key not found')
+        raise KeyError('Key not found')
diff --git a/solutions/object_oriented_design/lru_cache/lru_cache.ipynb b/solutions/object_oriented_design/lru_cache/lru_cache.ipynb
@@ -4,7 +4,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "This notebook was prepared by [Donne Martin](https://github.com/donnemartin). Source and license info is on [GitHub](https://github.com/donnemartin/system-design-primer-primer)."
+    "This notebook was prepared by [Donne Martin](https://github.com/donnemartin). Source and license info is on [GitHub](https://github.com/donnemartin/system-design-primer)."
    ]
   },
   {
@@ -21,7 +21,7 @@
     "## Constraints and assumptions\n",
     "\n",
     "* What are we caching?\n",
-    "    * We are cahing the results of web queries\n",
+    "    * We are caching the results of web queries\n",
     "* Can we assume inputs are valid or do we have to validate them?\n",
     "    * Assume they're valid\n",
     "* Can we assume this fits memory?\n",
@@ -56,7 +56,8 @@
     "\n",
     "    def __init__(self, results):\n",
     "        self.results = results\n",
-    "        self.next = next\n",
+    "        self.prev = None\n",
+    "        self.next = None\n",
     "\n",
     "\n",
     "class LinkedList(object):\n",
@@ -83,7 +84,7 @@
     "        \n",
     "        Accessing a node updates its position to the front of the LRU list.\n",
     "        \"\"\"\n",
-    "        node = self.lookup[query]\n",
+    "        node = self.lookup.get(query)\n",
     "        if node is None:\n",
     "            return None\n",
     "        self.linked_list.move_to_front(node)\n",
@@ -96,7 +97,7 @@
     "        If the entry is new and the cache is at capacity, removes the oldest entry\n",
     "        before the new entry is added.\n",
     "        \"\"\"\n",
-    "        node = self.lookup[query]\n",
+    "        node = self.lookup.get(query)\n",
     "        if node is not None:\n",
     "            # Key exists in cache, update the value\n",
     "            node.results = results\n",

diff --git a/solutions/object_oriented_design/lru_cache/lru_cache.py b/solutions/object_oriented_design/lru_cache/lru_cache.py
@@ -11,9 +11,14 @@ def __init__(self):
         self.head = None
         self.tail = None
 
-    def move_to_front(self, node):  # ...
-    def append_to_front(self, node):  # ...
-    def remove_from_tail(self):  # ...
+    def move_to_front(self, node):
+        pass
+
+    def append_to_front(self, node):
+        pass
+
+    def remove_from_tail(self):
+        pass
 
 
 class Cache(object):
@@ -24,25 +29,25 @@ def __init__(self, MAX_SIZE):
         self.lookup = {}  # key: query, value: node
         self.linked_list = LinkedList()
 
-    def get(self, query)
+    def get(self, query):
         """Get the stored query result from the cache.
-        
+
         Accessing a node updates its position to the front of the LRU list.
         """
-        node = self.lookup[query]
+        node = self.lookup.get(query)
         if node is None:
             return None
         self.linked_list.move_to_front(node)
         return node.results
 
     def set(self, results, query):
         """Set the result for the given query key in the cache.
-        
+
         When updating an entry, updates its position to the front of the LRU list.
         If the entry is new and the cache is at capacity, removes the oldest entry
         before the new entry is added.
         """
-        node = self.lookup[query]
+        node = self.lookup.get(query)
         if node is not None:
             # Key exists in cache, update the value
             node.results = results
@@ -58,4 +63,4 @@ def set(self, results, query):
             # Add the new key and value
             new_node = Node(results)
             self.linked_list.append_to_front(new_node)
-            self.lookup[query] = new_node
+            self.lookup[query] = new_node
diff --git a/solutions/object_oriented_design/online_chat/online_chat.ipynb b/solutions/object_oriented_design/online_chat/online_chat.ipynb
@@ -4,7 +4,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "This notebook was prepared by [Donne Martin](https://github.com/donnemartin). Source and license info is on [GitHub](https://github.com/donnemartin/system-design-primer-primer)."
+    "This notebook was prepared by [Donne Martin](https://github.com/donnemartin). Source and license info is on [GitHub](https://github.com/donnemartin/system-design-primer)."
    ]
   },
   {

diff --git a/solutions/object_oriented_design/online_chat/online_chat.py b/solutions/object_oriented_design/online_chat/online_chat.py
@@ -1,16 +1,26 @@
 from abc import ABCMeta
+from enum import Enum
 
 
 class UserService(object):
 
     def __init__(self):
         self.users_by_id = {}  # key: user id, value: User
 
-    def add_user(self, user_id, name, pass_hash):  # ...
-    def remove_user(self, user_id):  # ...
-    def add_friend_request(self, from_user_id, to_user_id):  # ...
-    def approve_friend_request(self, from_user_id, to_user_id):  # ...
-    def reject_friend_request(self, from_user_id, to_user_id):  # ...
+    def add_user(self, user_id, name, pass_hash):
+        pass
+
+    def remove_user(self, user_id):
+        pass
+
+    def add_friend_request(self, from_user_id, to_user_id):
+        pass
+
+    def approve_friend_request(self, from_user_id, to_user_id):
+        pass
+
+    def reject_friend_request(self, from_user_id, to_user_id):
+        pass
 
 
 class User(object):
@@ -25,12 +35,23 @@ def __init__(self, user_id, name, pass_hash):
         self.received_friend_requests_by_friend_id = {}  # key: friend id, value: AddRequest
         self.sent_friend_requests_by_friend_id = {}  # key: friend id, value: AddRequest
 
-    def message_user(self, friend_id, message):  # ...
-    def message_group(self, group_id, message):  # ...
-    def send_friend_request(self, friend_id):  # ...
-    def receive_friend_request(self, friend_id):  # ...
-    def approve_friend_request(self, friend_id):  # ...
-    def reject_friend_request(self, friend_id):  # ...
+    def message_user(self, friend_id, message):
+        pass
+
+    def message_group(self, group_id, message):
+        pass
+
+    def send_friend_request(self, friend_id):
+        pass
+
+    def receive_friend_request(self, friend_id):
+        pass
+
+    def approve_friend_request(self, friend_id):
+        pass
+
+    def reject_friend_request(self, friend_id):
+        pass
 
 
 class Chat(metaclass=ABCMeta):
@@ -51,8 +72,11 @@ def __init__(self, first_user, second_user):
 
 class GroupChat(Chat):
 
-    def add_user(self, user):  # ...
-    def remove_user(self, user):  # ... 
+    def add_user(self, user):
+        pass
+
+    def remove_user(self, user):
+        pass
 
 
 class Message(object):
@@ -77,4 +101,4 @@ class RequestStatus(Enum):
     UNREAD = 0
     READ = 1
     ACCEPTED = 2
-    REJECTED = 3
+    REJECTED = 3
diff --git a/solutions/object_oriented_design/parking_lot/parking_lot.ipynb b/solutions/object_oriented_design/parking_lot/parking_lot.ipynb
@@ -4,7 +4,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "This notebook was prepared by [Donne Martin](https://github.com/donnemartin). Source and license info is on [GitHub](https://github.com/donnemartin/system-design-primer-primer)."
+    "This notebook was prepared by [Donne Martin](https://github.com/donnemartin). Source and license info is on [GitHub](https://github.com/donnemartin/system-design-primer)."
    ]
   },
   {
@@ -71,7 +71,7 @@
     "    def __init__(self, vehicle_size, license_plate, spot_size):\n",
     "        self.vehicle_size = vehicle_size\n",
     "        self.license_plate = license_plate\n",
-    "        self.spot_size\n",
+    "        self.spot_size = spot_size\n",
     "        self.spots_taken = []\n",
     "\n",
     "    def clear_spots(self):\n",