## 为工程师准备的 50 道数据结构和算法面试题

There are a lot of computer science graduates and programmers applying for programming, coding, and software development roles at startups like Uber and Netflix; big organizations like AmazonMicrosoft, and Google; and service-based companies like Infosys or Luxsoft, but many of them have no idea of what kind of programming interview questions to expect when you’re applying for a job with these companies.

In this article, I’ll share some _frequently asked programming interview questions_from different interviews for programmers at different levels of experience, from people who have just graduated from college to programmers with one to two years of experience.

Coding interviews are comprised mainly of data structure and algorithm-based questions as well as some of the logical questions such as, How do you swap two integers without using a temporary variable?

I think it’s helpful to divide coding interview questions into different topic areas. The topic areas I’ve seen most often in interviews are array, linked list, string, binary tree, as well as questions from algorithms (e.g. string algorithm, sorting algorithms like quicksort or radix sort, and other miscellaneous ones), and that’s what you will find in this article.

It’s not guaranteed that you will be asked these coding or data structure and algorithmic questions, but they will give you enough of an idea of the kinds of questions you can expect in a real programming job interview.

Once you have gone through these questions, you should feel confident enough to attend any telephonic or face-to-face interviews.

Btw, there is no point in attempting these questions if you don’t have sufficient knowledge of essential Data Structure and Algorithms or you have not touched them from ages.

In that case, you should take a good course like Algorithms and Data Structures Part 1 and 2 By Robert Horvick to refresh your DS and algorithms skills.

### Top 50 Algorithms and Coding Interview Questions

Without any further ado, here is my list of some of the most frequently asked coding interview questions from programming job interviews:

### 1. Array Coding Interview Questions

An array is the most fundamental data structure, which stores elements at a contiguous memory location. It is also one of the darling topics of interviewers and you will hear a lot of questions about an array in any coding interview, e.g. reversing an array, sorting the array, or searching elements on the array.

The key benefit of an array data structure is that it offers fast O(1) search if you know the index, but adding and removing an element from an array is slow because you cannot change the size of the array once it’s created.

In order to create a shorter or longer array, you need to create a new array and copy all elements from old to new.

## 50个算法和代码面试题

### 1. 数组问题

The key to solving array-based questions is having a good knowledge of array data structure as well as basic programming constructors such as loop, recursion, and fundamental operators.

Here are some of the popular array-based coding interview questions for your practice:

1. How do you find the missing number in a given integer array of 1 to 100? (solution)

2. How do you find the duplicate number on a given integer array? (solution)

3. How do you find the largest and smallest number in an unsorted integer array? (solution)

4. How do you find all pairs of an integer array whose sum is equal to a given number? (solution)

5. How do you find duplicate numbers in an array if it contains multiple duplicates? (solution)

6. How are duplicates removed from a given array in Java? (solution)

7. How is an integer array sorted in place using the quicksort algorithm? (solution)

8. How do you remove duplicates from an array in place? (solution)

9. How do you reverse an array in place in Java? (solution)

10. How are duplicates removed from an array without using any library? (solution)

If you need more advanced questions based upon array then you can see also seeThe Coding Interview Bootcamp: Algorithms + Data Structures, a bootcamp style course on algorithms, especially designed for interview preparation to get a job on technical giants like Google, Microsoft, Apple, Facebook etc.

And, if you feel 10 is not enough questions and you need more practice, then you can also check out this list of 30 array questions.

1. 在一个给定的从1到100的整型数组中，如何快速找到缺失的数字？（解决方案

2. 如何找到一个给定的整型数组中的重复数字？（解决方案

3. 在一个未排序的整型数组中，如何找到最大和最小的数字？（解决方案

4. 在一个整型数组中，如何找到一个所有成对的数字，满足它们的和等于一个给定的数字？（解决方案

5. 如果一个数组包含多个重复元素，如何找到这些重复的数字？（解决方案

6. 用 Java 实现从一个给定数组中删除重复元素？（解决方案

7. 如何利用快速排序对一个整型数组进行排序？（解决方案

8. 如何从一个数组中删除重复元素？（解决方案

9. 用 Java 实现数组反转？（解决方案

10. 如何不借助库实现从数组中删除重复元素？（解决方案

### 2. Linked List Programming Interview Questions

linked list is another common data structure that complements the array data structure. Similar to the array, it is also a linear data structure and stores elements in a linear fashion.

However, unlike the array, it doesn’t store them in contiguous locations; instead, they are scattered everywhere in memory, which is connected to each other using nodes.

A linked list is nothing but a list of nodes where each node contains the value stored and the address of the next node.

### 2. 链表的编程问题

Because of this structure, it’s easy to add and remove elements in a linked list, as you just need to change the link instead of creating the array, but the search is difficult and often requires O(n) time to find an element in the singly linked list.

It also comes in varieties like a singly linked list, which allows you to traverse in one direction (forward or reverse); a doubly linked list, which allows you to traverse in both directions (forward and backward); and finally, the circular linked list, which forms a circle.

In order to solve linked list-based questions, a good knowledge of recursion is important, because a linked list is a recursive data structure.

If you take one node from a linked list, the remaining data structure is still a linked list, and because of that, many linked list problems have simpler recursive solutions than iterative ones.

Here are some of the most common and popular linked list interview questions and their solutions:

1. How do you find the middle element of a singly linked list in one pass? (solution)

2. How do you check if a given linked list contains a cycle? How do you find the starting node of the cycle? (solution)

3. How do you reverse a linked list? (solution)

4. How do you reverse a singly linked list without recursion? (solution)

5. How are duplicate nodes removed in an unsorted linked list? (solution)

6. How do you find the length of a singly linked list? (solution)

7. How do you find the third node from the end in a singly linked list? (solution)

8. How do you find the sum of two linked lists using Stack? (solution)

If you are having trouble solving these linked list coding questions then I suggest you refresh your data structure and algorithms skill by going through Data Structures and Algorithms: Deep Dive** Using Java** course.

You can also check out this list of30 linked list interview questions for more practice questions.

1. 在一次遍历中，怎样发现单个链表的中间元素? (答案)

2. 怎样验证给定的链表是环形的? 怎样发现这个环的起始节点? (答案)

3. 怎样翻转链表? (答案)

4. 不使用递归，怎样反转单个链表? (答案)

5. 在未排序链表中，怎样移除重复的节点? (答案)

6. 怎样找出单个链表的长度? (答案)

7. 从单个链表的结尾处，怎样找出链表的第三个节点? (答案)

8. 怎样使用栈计算两个链表的和? (答案)