Cracking the Coding Interview, 4 Edition - 150 Programming Interview Questions and Solutions

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Solutions to Chapter 18 | Threads and Locks 18.3 Implement a singleton design pattern as a template such that, for any given class Foo, you can call Singleton::instance() and get a pointer to an instance of a singleton of type Foo. Assume the existence of a class Lock which has acquire() and release() methods. How could you make your implementation thread safe and exception safe? SOLUTION 1 using namespace std; 2 /* Place holder for thread synchronization lock */ 3 class Lock { 4 public: 5 Lock() { /* placeholder code to create the lock */ } 6 ~Lock() { /* placeholder code to deallocate the lock */ } 7 void AcquireLock() { /* placeholder to acquire the lock */ } 8 void ReleaseLock() { /* placeholder to release the lock */ } 9 }; 10 11 /* Singleton class with a method that creates a new instance of the 12 * class of the type of the passed in template if it does not 13 * already exist. */ 14 template class Singleton { 15 private: 16 static Lock lock; 17 static T* object; 18 protected: 19 Singleton() { }; 20 public: 21 static T * instance(); 22 }; 23 Lock Singleton::lock; 24 25 T * Singleton::Instance() { 26 /* if object is not initialized, acquire lock */ 27 if (object == 0) { 28 lock.AcquireLock(); 29 /* If two threads simultaneously check and pass the first “if” 30 * condition, then only the one who acquired the lock first 31 * should create the instance */ 32 if (object == 0) { 33 object = new T; 34 } 35 lock.ReleaseLock(); 36 } 37 return object; 38 } pg 86 2 5 9 Cracking the Coding Interview | Knowledge Based
Solutions to Chapter 18 | Threads and Locks 39 40 int main() { 41 /* foo is any class defined for which we want singleton access */ 42 Foo* singleton_foo = Singleton::Instance(); 43 return 0; 44 } The general method to make a program thread safe is to lock shared resources whenever write permission is given. This way, if one thread is modifying the resource, other threads can not modify it. CareerCup.com 2 6 0
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CRACKING THE FOURTH EDITION C O D I
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Table of Contents Chapter 7 | Objec
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Introduction Something’s Wrong We
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Behind the Scenes For many candidat
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Behind the Scenes | The Amazon Inte
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Behind the Scenes | The Apple Inter
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Interview War Stories The View from
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Interview War Stories | Pop Divas P
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Interview War Stories | You Can (Ma
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Interview War Stories | Spider Sens
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Before the Interview | Resume Advic
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Before the Interview | Behavioral P
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Before the Interview | Technical Pr
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The Interview and Beyond
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At the Interview | Handling Behavio
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At the Interview | Handling Technic
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At the Interview | Five Algorithm A
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At the Interview | Five Algorithm A
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At the Interview | The Offer and Be
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At the Interview | Top Ten Mistakes
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At the Interview | Frequently Asked
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Interview Questions
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Chapter 1 | Arrays and Strings Hash
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Chapter 2 | Linked Lists How to App
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Chapter 3 | Stacks and Queues How t
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Chapter 4 | Trees and Graphs How to
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Part 2 Concepts and Algorithms
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Chapter 5 | Bit Manipulation 5.1 Yo
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Chapter 6 | Brain Teasers 6.1 Add a
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Chapter 7 | Object Oriented Design
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Chapter 8 | Recursion 8.1 Write a m
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Chapter 9 | Sorting and Searching 9
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Chapter 10 | Mathematical 10.1 You
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Chapter 11 | Testing 11.1 Find the
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Chapter 12 | System Design and Memo
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Chapter 13 | C++ How To Approach: A
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Chapter 14 | Java How to Approach:
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Chapter 15 | Databases How to Appro
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Chapter 16 | Low Level How to Appro
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Chapter 17 | Networking How to Appr
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Chapter 18 | Threads and Locks How
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Part 4 Additional Review Problems
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Chapter 19 | Moderate _____________
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Chapter 20 | Hard Input: DAMP, LIKE
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Solutions
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Solutions to Chapter 1 | Arrays and
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Solutions to Chapter 2 | Linked Lis
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Solutions to Chapter 3 | Stacks and
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Solutions to Chapter 4 | Trees and
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Solutions to Chapter 5 | Bit Manipu
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Solutions to Chapter 7 | Object Ori
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Solutions to Chapter 8 | Recursion
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Solutions to Chapter 9 | Sorting an
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Page 199 and 200: Solutions to Chapter 11 | System De
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Page 223 and 224: Solutions to Chapter 15 | Databases
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Page 241 and 242: Solutions to Chapter 17 | Networkin
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Page 291 and 292: Index A arithmetic 108, 131, 143, 1
Page 293: Mock Interviews Mock Interviews Stu
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