Control Flow

Exercises

If/else

pub fn bigger(a: i32, b: i32) -> i32 {
    // Complete this function to return the bigger number!
    // Do not use:
    // - another function call
    // - additional variables
}

// Don't mind this for now :)
#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn ten_is_bigger_than_eight() {
        assert_eq!(10, bigger(10, 8));
    }

    #[test]
    fn fortytwo_is_bigger_than_thirtytwo() {
        assert_eq!(42, bigger(32, 42));
    }
}

#![allow(unused)]
fn main() {
pub fn bigger(a: i32, b: i32) -> i32 {
  if a > b {
      a
  } else {
      b
  }
}

// Don't mind this for now :)
#[cfg(test)]
mod tests {
  use super::*;

  #[test]
  fn ten_is_bigger_than_eight() {
      assert_eq!(10, bigger(10, 8));
  }

  #[test]
  fn fortytwo_is_bigger_than_thirtytwo() {
      assert_eq!(42, bigger(32, 42));
  }
}
}

Loop

use num::integer::sqrt;

// There's a prime number hiding in our array of integers!
// The function below tries to find the prime number by checking each element,
// and finding its divisor. If none is found, then it's a prime number and
// its search ends!

// But it seems that its search never does end, when there's clearly a
// prime number there. Fix the function so that it returns the prime number.

fn main() {
    let numbers = [36, 25, 49, 3, 64, 16, 9];
    let prime = get_prime(numbers);
}

fn get_prime(arr: [i32; 7]) -> i32 {

    // Loop through every element in the array
    let mut i = 0;
    'outer: loop {

        // Find a divisor.
        let mut n = 2;
        'inner: loop {
            
            // If a number can be evenly divided by another number except 1 and itself,
            // then it's not a prime.
            // Break out here to move on to the next element.
            if arr[i] % n == 0 {
                if arr[i] == 2 {
                    break 'outer;
                }
                i += 1;
                break;
            }

            // If no divisors are found, then we've found a prime!
            // Break out of the loop here.
            if n >= sqrt(arr[i]) {
                break;
            }
            
            // Otherwise, move to the next element.
            n += 1;
        }
    }
    println!("The first prime number in the array is {}.", arr[i]);
    arr[i]
}

use num::integer::sqrt;

fn main() {
  let numbers = [36, 25, 49, 3, 64, 16, 9];
  let prime = get_prime(numbers);
}

fn get_prime(arr: [i32; 7]) -> i32 {

  let mut i = 0;
  'outer: loop {

      let mut n = 2;
      'inner: loop {
          
          if arr[i] % n == 0 {
              if arr[i] == 2 {
                  break 'outer;
              }
              i += 1;
              break;
          }

          if n >= sqrt(arr[i]) {
              break 'outer;
          }
          
          n += 1;
      }
  }
  println!("The first prime number in the array is {}.", arr[i]);
  arr[i]
}

While

// Below is the classic FizzBuzz program. It prints every number from 1 to 100,
// except for multiples of 3 it prints "fizz" instead of the number, and for
// multiples of 5 it prints "buzz" instead of the number. If the number is
// both a multiple of 3 and 5, it prints "fizzbuzz".

// Fix the compile time error so that the program runs successfully.

fn main() {
    let mut n = 1;
    while {
        if n % 15 == 0 {
            println!("fizzbuzz");
        } else if n % 3 == 0 {
            println!("fizz");
        } else if n % 5 == 0 {
            println!("buzz");
        } else {
            println!("{}", n);
        }
        n += 1;
    }
}

fn main() {
  let mut n = 1;
  while n <= 100 {
      if n % 15 == 0 {
          println!("fizzbuzz");
      } else if n % 3 == 0 {
          println!("fizz");
      } else if n % 5 == 0 {
          println!("buzz");
      } else {
          println!("{}", n);
      }
      n += 1;
  }
}

For

// Here's a bucket list of cities I'd like to visit one day, and I'd like to
// share it with the world. Fix the loop so it announces the cities I'd like to visit.

fn main() {
    let cities = ["Perth", "Qingdao", "Rome"];
    for cities {
        println!("I'd like to visit {} someday!", city);
    }
}

fn main() {
  let cities = ["Perth", "Qingdao", "Rome"];
  for city in cities {
      println!("I'd like to visit {} someday!", city);
  }
}