Sorting an associative array by key fails

[hancooper]

I am populating an associative array, which I want to sort later by key for 
display purposes.

The sort will fail with the following code, because the sort gives

1-0
1-12
1-15
1-18
1-21
1-24
1-27
1-3
1-30
1-33
1-36
1-39
1-42
1-45
1-48
1-51
1-54
1-57
1-6
1-9

Somehow I need a function that I can pass a numeric value and returns me a 
string with
a tho appropriate nember of zeroes appended at the beginning (e.g. to get 1-00, 
1-01, 1.02, ... ).

Here is the code.

local i
declare -A asc
for (( i = 0; i < ndlc; i++ )); do
k=$(( (i % nproc) + 1 ))
elm=${dlc[$i]} ; elm=${elm#*$'\t'} # remove size entry
asc[$k-$i]="$elm" # set dir name
(( vb >=3 )) && echo "asc[$k-$i]=dlc[$i]"
done