updated interview notes

Author: jasonzhuyx

docs/aws-study.md

@@ -6,11 +6,19 @@
 
 ## Content
 
+  * [CloudFormation](#cf)
   * [RDS - MySQL](#rds)
   * [EC2](#ec2)
 
 
 
+</br><a name="cf"></a>
+## AWS CloudFormation
+
+  * [Sceptre](https://github.com/Sceptre/sceptre) is a tool to drive
+    [AWS CloudFormation](https://aws.amazon.com/cloudformation)
+
+
 </br><a name="rds"></a>
 ## AWS RDS
 

docs/interview.md

@@ -178,6 +178,8 @@
 <a name="design-db"></a>
 ### Database Design
 
+#### Concepts
+
   * ACID
     - **Atomicity**: Transactions are often composed of multiple statements. Atomicity guarantees that each transaction is treated as a single "unit", which either succeeds completely, or fails completely: if any of the statements constituting a transaction fails to complete, the entire transaction fails and the database is left unchanged. An atomic system must guarantee atomicity in each and every situation, including power failures, errors and crashes.
 
@@ -187,10 +189,61 @@
 
     - **Durability**: guarantees that once a transaction has been committed, it will remain committed even in the case of a system failure (e.g., power outage or crash). This usually means that completed transactions (or their effects) are recorded in non-volatile memory.
 
+#### SQL Query
+
+  * For DB tables:
+
+    ```sql
+    -- containers(id, name);
+    CREATE TABLE IF NOT EXISTS containers (
+      `id` INT NOT NULL AUTO_INCREMENT COMMENT 'PK for containers',
+      `name` VARCHAR(45) NULL COMMENT 'container name',
+      PRIMARY KEY (`id`)
+    );
+
+    -- items(id, type);
+    CREATE TABLE IF NOT EXISTS items (
+      `id` INT NOT NULL AUTO_INCREMENT COMMENT 'PK for items',
+      `type` VARCHAR(45) NULL COMMENT 'Item type',
+      PRIMARY KEY (`id`)
+    );
+
+    -- containeritem(container_id, item_id);
+    CREATE TABLE IF NOT EXISTS containeritem (
+      `container_id` INT NOT NULL COMMENT 'Composite PK: FK to containers.id',
+      `item_id` INT NOT NULL COMMENT 'Composite PK: FK to items.id',
+      CONSTRAINT `FK__containeritem_container_id`
+        FOREIGN KEY (`container_id`)
+        REFERENCES `containers` (`id`),
+      CONSTRAINT `FK__containeritem_item_id`
+        FOREIGN KEY (`item_id`)
+        REFERENCES `items` (`id`)
+    );
+    ```
+    Write a SQL query to list all container names, item types, and count of types (including zero) for each container.
+
+    ```sql
+    SELECT d.name, d.type,
+      CASE WHEN ci.item_id IS NULL THEN 0 ELSE count(ci.item_id) END as 'count'
+      FROM (
+      SELECT c.id as 'c_id', c.name, i.id as 'i_id', i.type
+        FROM containers c
+       CROSS JOIN items i
+      ) d  -- optionally to use CTE
+     LEFT OUTER JOIN containeritem ci ON d.i_id = ci.item_id
+      AND d.c_id = ci.container_id
+     GROUP BY d.name, d.type
+     ORDER BY d.name, d.type
+    ;
+    ```
+    See http://sqlfiddle.com/#!9/20fa2b/52
+
 
 <a name="design-system"></a>
 ### System Design
 
+#### Checklist
+
   * A.B.C.D.
     - **_A_**sk questions (what features? how much to scale? ...)
     - Don't use **_b_**uzzword
@@ -287,6 +340,31 @@
     * HAProxy
 
 
+#### Example: Find the peakest time
+
+  From a long list of trip time (with Start and End time, sorted by Started), e.g. within a whole month, find the peakest trip time.¶
+
+  ```go
+  type Trip struct {
+    Start time
+    End time
+  }
+
+  // assuming the list (e.g. a whole month/year) is sorted by start time
+  func countPeakTrips(a []Trip) int {
+
+  }
+  ```
+
+
+#### Example: Design a stock data system
+
+  * requirements
+    - get real time price
+    - get historic trend
+  * data schema and database
+  * misc consideration
+
 
 ### Resources:
 
@@ -575,7 +653,7 @@
 
 
 <br/><a name="non-tech"></a>
-### Non-technical
+## Non-technical
 
   * [Psychological Tricks](https://github.com/yangshun/tech-interview-handbook/blob/master/non-technical/psychological-tricks.md)
   * [Questions to ask](https://github.com/yangshun/tech-interview-handbook/blob/master/non-technical/questions-to-ask.md)
@@ -584,7 +662,7 @@
 
 
 <br/><a name="reading"></a>
-### Reading
+## Reading
 
 * Books/Collection:
   * [Computer Science in JavaScript](https://github.com/humanwhocodes/computer-science-in-javascript)

docs/karat.md

@@ -7,6 +7,7 @@
 
 * [Karat Technical Categories](#categories)
 * [Karat Coding Questions](#coding)
+* [Miscellaneous](#misc)
 
 
 <br /><a name="categories"></a>
@@ -42,6 +43,11 @@
 * Testing
   * What is race condition and how it happens?
 
+* Others
+  - Know Graph very well. Read a lot of graph problems from leet code and geek for geeks.
+
+
+
 
 <br /><a name="coding"></a>
 ## Karat Coding
@@ -140,3 +146,19 @@
   ranges = getMostBookedRanges(workers)
   # expecting [(2, 3), (4, 6)]
   ```
+
+
+<br /><a name="misc"></a>
+## Miscellaneous
+
+  * Open questions:
+    - How would you explain Google to your grandmother?
+    - How would you teach her to fix her Facebook if there was an error or malfunction?
+    - What's something your building? What's an ecommerce company you use?   
+
+  * Others
+    - Given an array of fruits and an other array weights of fruits, write a function to pick the fruits randomly with a probability distribution equal to its weights.
+    - Given a graph and a node in the graph, return a deep copy of the node.
+    - Given a frequency distribution of objects, write a random object generator which produces objects based on their probability distribution.
+    - Given a binary tree with parent pointers (pointers that direct from leaves to the root), design an O(1) space complexity algorithm to find the lowest common ancestor of any two nodes.
+    - Evaluate an arithmetic expression that only involves multiplication and addition.   

ml/README.md

@@ -6,3 +6,20 @@
 ## Contents
 
 * [Design API Server](./api/README.md)
+
+
+
+<br/>
+
+```
+-+++++=        .+++++=
+.+@@@@@+       #@@@@*:
+  .@@@@@=     *@@@@@  
+   @+@@@@-   =#@@@@@  
+   @ +@@@@: :% @@@@@  
+   @  *@@@@-%: @@@@@  
+   @   *@@@@-  @@@@@  
+  -@-   #@@+  :@@@@@:
+-#@@@#-  ##  =@@@@@@@=
+.......      .........
+```