Difference of Squares in Rust

문제

참고할 자료와 개념

• Learn Rust in Y Minutes

for 문

• 1..n과 1..=n의 차이
• The Rust Programming Language
  • ch3 Common Programming Concepts
• Easy Rust
  • Easy Rust - 27.Loops
  • 유튜브, 프로그래밍 언어 러스트를 배웁시다! 037 Easy Rust in Korean: Loops

(심화) iterator, closure, map, sum

• The Rust Programming Language
  • 13.1 Closures: Anonymous Functions that Capture Their Environment
  • 13.2 Processing a Series of Items with Iterators
  • 13.4 Comparing Performance: Loops vs. Iterators
  • Appendix B: Operators and Symbols
• Easy Rust
  • 37.Itertors
  • 유튜브, 070 Easy Rust in Korean: Iterators and assert_eq!
  • 38.Closures
  • 유튜브, 072 Easy Rust in Korean: Intro to closures

풀이된 예제

명령형

pub fn square_of_sum(n: u32) -> u32 {
    let mut sum = 0;
    for i in 1..=n {
        sum += i;
    }
    sum * sum
}

pub fn sum_of_squares(n: u32) -> u32 {
    let mut sum = 0;
    for i in 1..=n {
        sum += i * i;
    }
    sum
}

pub fn difference(n: u32) -> u32 {
    square_of_sum(n) - sum_of_squares(n)
}

함수형 이터레이터

pub fn square_of_sum(n: u32) -> u32 {
    (1..=n).sum::<u32>().pow(2)
}

pub fn sum_of_squares(n: u32) -> u32 {
    (1..=n).map(|x| x.pow(2)).sum()
}

pub fn difference(n: u32) -> u32 {
    square_of_sum(n) - sum_of_squares(n)
}

수학

• 수학방 : 등차수열의 합 공식
• 수학방 : 자연수 거듭제곱의 합 공식, 유도

pub fn square_of_sum(n: u32) -> u32 {
    (n * (n + 1) / 2).pow(2)
}

pub fn sum_of_squares(n: u32) -> u32 {
    n * (n + 1) * (2 * n + 1) / 6
}

pub fn difference(n: u32) -> u32 {
    square_of_sum(n) - sum_of_squares(n)
}