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Attempting to solve the "Lonely Integer" problem

HackerRank problem statement: enter image description here

My solution

declare -i n
read n
declare -a numbers
read numbers
n=${#numbers[@]}-1
while [ $n -ge 0 ]; do echo "${numbers[$n]}\n"; ((n--)); done | sort -n | uniq -u

Except the bash on the HackerRank IDE which is 5.2.32 ( tested with bash --version ) throws the following error

enter image description here

P.S. ( When I tested the script on my end I used the shebang #!/bin/bash, the IDE does not require that, please don't say that is the solution )

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13
  • 2
    [ doesn't do arithmetic. 1-1 isn't a valid number. Commented Oct 8 at 21:17
  • 2
    read numbers will not read each number into a different element of the array. See stackoverflow.com/questions/9293887/… Commented Oct 8 at 21:23
  • 2
    You can use n=$((${#numbers[@]}-1)) to perform arithmetic in bash. Commented Oct 8 at 21:24
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    Ah, I guess you're using a newer Bash whose declare -i causes n=1-1 to do arithmetic evaluation, but the target system does not. More minimal example: declare -i n; n=1-1; echo $n. I think you can reduce this question greatly (and get rid of the images). Commented Oct 9 at 9:19
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    @Barmar, assignment does do arithmetic, when declare -i has been used. Commented Oct 9 at 9:35

1 Answer 1

Reset to default
2

I think the target shell isn't behaving according to Bash documentation, and that can be demonstrated more simply:

#!/usr/bin/bash
declare -i n
n=1-1
echo $n

declare -i is documented as:

The variable is treated as an integer; arithmetic evaluation (see ARITHMETIC EVALUATION above) is performed when the variable is assigned a value.

You can make the code portable/resilient by explicitly asking for arithmetic expansion:

n=$((1-1))

In your program, you don't need n though, since you just want to expand the entire array:

read  # ignore first line
read -a numbers
printf '%d\n' "${numbers[@]}" | sort -n | uniq -u
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1 Comment

Ty -- I tried to get printf to work that way but it was not printing it out in different lines in the target shell i.e. HackerRank IDE -- also some of my solutions were failing but when I tried the exact same solution again by literally running the code saved on the IDE, which was failing earlier somehow, it passed; so I believe the hacker rank IDE is just extremely buggy.

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