# Created on savesnippets.com · https://savesnippets.com/LzNcS9fvIxb54g
input=(apple banana apple cherry banana date apple)

dedupe() {
    declare -A seen=()
    local out=()
    for item in "$@"; do
        if [[ -z "${seen[$item]+x}" ]]; then
            seen[$item]=1
            out+=("$item")
        fi
    done
    printf '%s\n' "${out[@]}"
}

dedupe "${input[@]}"
# apple
# banana
# cherry
# date