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collections.md

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Header

This is the course header. This will be added on top of every page. Go to DoDAO.io to know more.

Collections

Where in the mempry are colections stored
  • Stack
  • Program Area
  • Heap

Hint: NoHint

Explanation: Collections are dynamically sized ans tored on heap.

Sub Topics: collection_introduction

What is the output of the following code snippet:
``` 
    let v = Vec![1,2,3,4,5];
    let third = &v[10];

    println!(“The third element is {}”, third);
```
  • It prints None
  • It does not print anything
  • It prints 5
  • It will resume in panic

Hint: NoHint

Explanation: Trying to index vector outside it boundries result in panic.

Sub Topics: collection_vector

What is the output of the following code snippet:
``` 
    let v = Vec![1,2,3,4,5];
    let third = v.get(2);

    println!(“The third element is {}”, third);
```
  • It prints None
  • It does not print anything
  • It prints 5
  • It will resume in panic

Hint: NoHint

Explanation: Trying to index vector outside it boundries result in panic.

Sub Topics: collection_vector

Strings in Rust support which encoding:
  • UTF-8
  • Unicode
  • ASCII
  • UTF-32

Hint: NoHint

Explanation: Strings in Rust support UTF-8 encoding.

Sub Topics: collection_strings

What is the output of the following code snippet:
``` 
    let s1 = “Hello, “;
    let s2 = “world!“;
    let s3 = s1 + &s2;

    println!(s1 is {}”, s1);
```
  • Program will not compile
  • It prints Hello,
  • It prints Hello, world!
  • It prints None

Hint: NoHint

Explanation: When using + macro first argument is moved and not accessible after that.

Sub Topics: collection_strings

How can strings be indexed in Rust ?
  • str[1]
  • String indexing does not works in Rust
  • str.1
  • str.get(1)

Hint: NoHint

Explanation: String indexing is not allowed in Rust.

Sub Topics: collection_strings

Which hashmap method can be used to add an entry to map only if it does not already exists ?
  • insert
  • push
  • or_insert
  • insert_or

Hint: NoHint

Explanation: or_insert will insert an entry into HashMap only if it does not already exist.

Sub Topics: collection_hashmap

Which of the following are methods available on Vectors ?
  • len
  • length
  • replace
  • push

Hint: NoHint

Explanation: Methods len and push are available on Vectors.

Sub Topics: collection_vector

Vectors and HashMap needs to be explicitly included in the scope.
  • True
  • False

Hint: NoHint

Explanation: Only HashMap need to be explicitly included in the scope.

Sub Topics: collection_vector

Which of the following are methods available on Strings ?
  • index
  • length
  • contains
  • trim

Hint: NoHint

Explanation: Methods contains and trim are available on Strings.

Sub Topics: collection_vector