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magandrez's solution

to Raindrops in the Bash Track

Published at Jan 30 2019 · 0 comments
Instructions
Test suite
Solution

Note:

This exercise has changed since this solution was written.

Convert a number to a string, the contents of which depend on the number's factors.

  • If the number has 3 as a factor, output 'Pling'.
  • If the number has 5 as a factor, output 'Plang'.
  • If the number has 7 as a factor, output 'Plong'.
  • If the number does not have 3, 5, or 7 as a factor, just pass the number's digits straight through.

Examples

  • 28's factors are 1, 2, 4, 7, 14, 28.
    • In raindrop-speak, this would be a simple "Plong".
  • 30's factors are 1, 2, 3, 5, 6, 10, 15, 30.
    • In raindrop-speak, this would be a "PlingPlang".
  • 34 has four factors: 1, 2, 17, and 34.
    • In raindrop-speak, this would be "34".

Run the tests with:

bats raindrops_test.sh

After the first test(s) pass, continue by commenting out or removing the skip annotations prepending other tests.

Source

A variation on a famous interview question intended to weed out potential candidates. http://jumpstartlab.com

External utilities

Bash is a language to write scripts that works closely with various system utilities, like sed, awk, date and even other programming languages, like Python. This track does not restrict the usage of these utilities, and as long as your solution is portable between systems and does not require installing third party applications, feel free to use them to solve the exercise.

For an extra challenge, if you would like to have a better understanding of the language, try to re-implement the solution in pure Bash, without using any external tools.

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

raindrops_test.sh

#!/usr/bin/env bash

@test "the sound for 1 is 1" {
  #skip
  run bash raindrops.sh 1
  [ "$status" -eq 0 ]
  [ "$output" == "1" ]
}

@test "the sound for 3 is Pling" {
  skip
  run bash raindrops.sh 3
  [ "$status" -eq 0 ]
  [ "$output" == "Pling" ]
}

@test "the sound for 5 is Plang" {
  skip
  run bash raindrops.sh 5
  [ "$status" -eq 0 ]
  [ "$output" == "Plang" ]
}

@test "the sound for 7 is Plong" {
  skip
  run bash raindrops.sh 7
  [ "$status" -eq 0 ]
  [ "$output" == "Plong" ]
}

@test "the sound for 6 is Pling as it has a factor 3" {
  skip
  run bash raindrops.sh 6
  [ "$status" -eq 0 ]
  [ "$output" == "Pling" ]
}

@test "2 to the power 3 does not make a raindrop sound as 3 is the exponent not the base" {
  skip
  run bash raindrops.sh 8
  [ "$status" -eq 0 ]
  [ "$output" == "8" ]
}

@test "the sound for 9 is Pling as it has a factor 3" {
  skip
  run bash raindrops.sh 9
  [ "$status" -eq 0 ]
  [ "$output" == "Pling" ]
}

@test "the sound for 10 is Plang as it has a factor 5" {
  skip
  run bash raindrops.sh 10
  [ "$status" -eq 0 ]
  [ "$output" == "Plang" ]
}

@test "the sound for 14 is Plong as it has a factor of 7" {
  skip
  run bash raindrops.sh 14
  [ "$status" -eq 0 ]
  [ "$output" == "Plong" ]
}

@test "the sound for 15 is PlingPlang as it has factors 3 and 5" {
  skip
  run bash raindrops.sh 15
  [ "$status" -eq 0 ]
  [ "$output" == "PlingPlang" ]
}

@test "the sound for 21 is PlingPlong as it has factors 3 and 7" {
  skip
  run bash raindrops.sh 21
  [ "$status" -eq 0 ]
  [ "$output" == "PlingPlong" ]
}

@test "the sound for 25 is Plang as it has a factor 5" {
  skip
  run bash raindrops.sh 25
  [ "$status" -eq 0 ]
  [ "$output" == "Plang" ]
}

@test "the sound for 27 is Pling as it has a factor 3" {
  skip
  run bash raindrops.sh 27
  [ "$status" -eq 0 ]
  [ "$output" == "Pling" ]
}

@test "the sound for 35 is PlangPlong as it has factors 5 and 7" {
  skip
  run bash raindrops.sh 35
  [ "$status" -eq 0 ]
  [ "$output" == "PlangPlong" ]
}

@test "the sound for 49 is Plong as it has a factor 7" {
  skip
  run bash raindrops.sh 49
  [ "$status" -eq 0 ]
  [ "$output" == "Plong" ]
}

@test "the sound for 52 is 52" {
  skip
  run bash raindrops.sh 52
  [ "$status" -eq 0 ]
  [ "$output" == "52" ]
}

@test "the sound for 105 is PlingPlangPlong as it has factors 3, 5 and 7" {
  skip
  run bash raindrops.sh 105
  [ "$status" -eq 0 ]
  [ "$output" == "PlingPlangPlong" ]
}

@test "the sound for 3125 is Plang as it has a factor 5" {
  skip
  run bash raindrops.sh 3125
  [ "$status" -eq 0 ]
  [ "$output" == "Plang" ]
}
#!/usr/bin/env bash

set -o errexit

USAGE="Usage: raindrops.sh <integer>"

validate_args(){

    if [ "$#" -ne 1 ]
    then
	echo "$USAGE"
	exit 1
    elif ! [ "$1" -eq "$1" ] 2>/dev/null
    then
	echo "$USAGE"
	exit 1
    fi
}

run(){
    num="$1"
    factors=()
    if [ "$num" -eq 1 ]
    then
        echo -n "1"
        exit 0
    else
        # Calculate the factors
	for (( i=2; i<="$1"; i++ ));do
	    while [ $((num%i)) == 0 ];do
                # Store in an array each of the factors we want to work with
                # Note the space after each of 'em.
                case "$i" in
		    1) factors+=("1")
		       ;;
		    3) factors+=("Pling")
		       ;;
		    5) factors+=("Plang")
		       ;;
		    7) factors+=("Plong")
		       ;;
                    *) # do nothing
                       ;;
		esac
		num=$((num/i))
	    done
	done
    fi
    # Loops the factors obtained to form a string
    # dropping all duplicates.
    # This relies in the factors being factorised
    # as they appear (in order). Valid assumption?
    for i in "${factors[@]}";
    do
        if [[ "$drops" =~ $i ]]; then
            continue
        else
            #Concat
            drops="$drops$i"
        fi
    done
    # If empty, default to the number pass (does not have factors -> return number)
    echo "${drops-$1}"
}

main(){
    validate_args "$@"
    run "$@"
}

main "$@"

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magandrez's Reflection

Handcrafted and not very elegant, but gets the job done.