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Summary - Vectors

Combine push, get and for to build a shopping cart.

Vectors summary

Vec<T> is a growable array living on the heap. Creating: Vec::new(), vec![..], vec![x; n], with_capacity. Changing: push, pop (Option), insert, remove, extend, clear. Reading: v[i] (panic risk) or get (Option). Looping: &v reads, &mut v modifies, v consumes.

Sorting and filtering

Useful methods that work in place:

let mut v = vec![5, 3, 8, 3, 1, 8];
v.sort();                  // [1, 3, 3, 5, 8, 8]
v.dedup();                 // [1, 3, 5, 8]
v.retain(|&x| x > 2);      // [3, 5, 8]
v.reverse();               // [8, 5, 3]

Floating-point numbers can't be sorted with sort (because of NaN); v.sort_by(|a, b| a.total_cmp(b)) is used.

Practice Clean and filter

For let mut v = vec![5, 3, 8, 3, 1, 8];, apply sort, dedup and retain(|&x| x > 2) in order; print the result with {:?}.

Starter code

main.rs
fn main() {
    // buraya yaz
}

Sample solution

main.rs
fn main() {
    let mut v = vec![5, 3, 8, 3, 1, 8];
    v.sort();
    v.dedup();
    v.retain(|&x| x > 2);
    println!("{:?}", v);
}

Expected output

[3, 5, 8]

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 What is <code>v</code> after <code>let mut v = vec![3, 1, 3, 2]; v.sort(); v.dedup();</code>?

  • [1, 3, 2]
  • [1, 2, 3] Correct answer
  • [1, 2, 3, 3]
  • [3, 1, 2]

Explanation: dedup only removes consecutive duplicates, which is why sort is needed first.

2 Keep by condition

Question 
let mut v = vec![1, 3, 5, 8];
v.____(|&x| x > 2);   // [3, 5, 8]
Answer 
let mut v = vec![1, 3, 5, 8];
v.retain(|&x| x > 2);   // [3, 5, 8]

Explanation: retain keeps the elements that satisfy the condition, in place.

3 Method and effect

Term Meaning
sort() Ascending
dedup() Removes consecutive duplicates
retain(..) Keeps matching ones
reverse() Reverses the order

All lessons in Beginner

1 Rust basics

  1. What is Rust?
  2. Project with Cargo
  3. Your first program
  4. println! and formatting
  5. Comments
  6. Summary - Rust basics

2 Variables

  1. Variables with let
  2. Mutability with mut
  3. Constants with const
  4. Static variables
  5. Shadowing
  6. Summary - Variables

3 Data types

  1. Integers
  2. Floating point
  3. Bool and char
  4. Tuple
  5. Array
  6. Summary - Data types

4 Strings

  1. &str vs String
  2. Creating a String
  3. Concatenating strings
  4. format! macro
  5. String length
  6. Summary - Strings

5 Project: Calculator

  1. Project skeleton
  2. Reading input
  3. Computing
  4. Error handling
  5. Loop and exit

6 Functions

  1. Defining with fn
  2. Parameters
  3. Return value
  4. Expressions and statements
  5. Early return
  6. Summary - Functions

7 Control flow

  1. if-else
  2. match basics
  3. loop
  4. while loop
  5. for loop
  6. Summary - Control flow

8 Ownership

  1. What is ownership?
  2. Move semantics
  3. Copy trait
  4. Functions and ownership
  5. Return and ownership
  6. Summary - Ownership

9 Borrowing

  1. References
  2. Mutable reference
  3. Borrowing rules
  4. Dangling reference
  5. References and functions
  6. Summary - Borrowing

10 Slices

  1. String slices
  2. Slice syntax
  3. Array slices
  4. Slices and functions
  5. Range types
  6. Summary - Slices

11 Project: Guessing game

  1. Game skeleton
  2. Reading input
  3. Comparing numbers
  4. Random number
  5. Loop and exit

12 Structs

  1. Struct definition
  2. Creating an instance
  3. Tuple struct
  4. Unit-like struct
  5. Field update
  6. Summary - Structs

13 Methods

  1. impl block
  2. self parameter
  3. &mut self
  4. Associated functions
  5. Multiple impl blocks
  6. Summary - Methods

14 Enums

  1. Enum definition
  2. Variants
  3. Variants with data
  4. Option<T>
  5. Option instead of null
  6. Summary - Enums

15 Pattern matching

  1. match patterns
  2. Value binding
  3. if let
  4. while let
  5. _ wildcard
  6. Summary - Pattern matching

16 Project: To-do CLI

  1. Task model
  2. Adding
  3. Listing
  4. Marking done
  5. Reading commands

17 Vectors

  1. Vec<T>
  2. Push and pop
  3. Index and get
  4. Looping a vector
  5. with_capacity
  6. Summary - Vectors

18 Advanced strings

  1. String and &str conversion
  2. chars and bytes
  3. Slicing strings
  4. contains and replace
  5. split and join
  6. Summary - Advanced strings

19 Error handling

  1. Result<T, E>
  2. panic!
  3. ? operator
  4. match and Result
  5. unwrap and expect
  6. Summary - Error handling

20 Beginner final

  1. Vowel counter
  2. Average calculator
  3. Bank account
  4. Temperature converter