read N
readarray numbers
printf "%s\n" ${numbers[@]} | sort -rn | uniq -u

read N
read -a arr

# We create the variable found to help us iterate
found=0
while [[ ${#arr[@]} -gt 1 ]]; do
    # We create an array with the existent indexes
    idx=()
    for i in ${!arr[@]}; do
        idx+=("$i")
    done
    
    # We pick the first value
    check=${arr[${idx[$found]}]}
    
    # We start the counter of matches
    count=0
    
    # We check the array counting matches
    for i in ${!arr[@]}; do
        if [[ "${arr[$i]}" -eq "$check" ]]; then
            ((count++))
        fi
    done
    
    # We check how many matches we have
    if [[ $count -eq 2 ]]; then
        # If we have 2 matcher, we delete ALL matches
        for i in ${!arr[@]}; do
            if [[ "${arr[$i]}" -eq "$check" ]]; then
                unset arr[$i]
            fi
        done
    else
        # Else, we have 1 match, aka the lonely integer
        # We increase the found, so the check value skips the one
        ((found++))
    fi
done
echo "${arr[@]}"

#!/bin/sh

read dummy
read -a ARRAY
FILTER=()

# X (listof X) -> Boolean
member () {
  for i in ${@:2}; do
    if [[ $1 -eq $i ]]; then
        return 0
    fi
  done
  return 1
}

# X (listof X) -> (listof X)
filter () {
  new=()
  for i in ${@:2}; do
    if ! [[ $i -eq $1 ]]; then
        new+=($i)
    fi
  done
  # bash functions don't return values, so we use global vars instead
  FILTER=${new[@]}
}

# (listof X) -> X
lonelyint () {
  # () to properly create an array from element
  array=("$@")
  count=0

  for current in ${array[@]}; do
    let 'count++'
    rest=${array[@]:$count}
    if member $current $rest; then
        # this filter doesn't really work
        # array=(2 32 2) current=2 => array=(3)
        #new=${array[@]/$current/}
        filter $current ${array[@]}
        lonelyint ${FILTER[@]}
    else
        echo "$current"
        exit 0
    fi
  done
}

lonelyint ${ARRAY[@]}