How to add a value into the middle of an array? - arrays

Question

Hello I have the following array:
array=(1 2 3 4 5 7 8 9 12 13)
I execute this for loop:
for w in ${!array[#]}
do
comp=$(echo "${array[w+1]} - ${array[w]} " | bc)
if [ $comp = 1 ]; then
/*???*/
else
/*???*/
fi
done
What I would like to do is to insert a value when the difference between two consecutive elements is not = 1
How can I do it?
Many thanks.

Answer 1

Just create a loop from the minimum to the maximum values and fill the gaps:
array=(1 2 3 4 5 7 8 9 12 13)
min=${array[0]}
max=${array[-1]}
new_array=()
for ((i=min; i<=max; i++)); do
if [[ " ${array[#]} " =~ " $i " ]]; then
new_array+=($i)
else
new_array+=(0)
fi
done
echo "${new_array[#]}"
This creates a new array $new_array with the values:
1 2 3 4 5 0 7 8 9 0 0 12 13
This uses the trick in Check if an array contains a value.

Answer 2

You can select parts of the original array with ${arr[#]:index:count}.
Select the start, insert a new element, add the end.
To insert an element after index i=5 (the fifth element)
$ array=(1 2 3 4 5 7 8 9 12 13)
$ i=5
$ arr=("${array[#]:0:i}") ### take the start of the array.
$ arr+=( 0 ) ### add a new value ( may use $((i+1)) )
$ arr+=("${array[#]:i}") ### copy the tail of the array.
$ array=("${arr[#]}") ### transfer the corrected array.
$ printf '<%s>' "${array[#]}"; echo
<1><2><3><4><5><6><7><8><9><12><13>
To process all the elements, just do a loop:
#!/bin/bash
array=(1 2 3 4 5 7 8 9 12 13)
for (( i=1;i<${#array[#]};i++)); do
if (( array[i] != i+1 ));
then arr=("${array[#]:0:i}") ### take the start of the array.
arr+=( "0" ) ### add a new value
arr+=("${array[#]:i}") ### copy the tail of the array.
# echo "head $i ${array[#]:0:i}" ### see the array.
# echo "tail $i ${array[#]:i}"
array=("${arr[#]}") ### transfer the corrected array.
fi
done
printf '<%s>' "${array[#]}"; echo
$ chmod u+x ./script.sh
$ ./script.sh
<1><2><3><4><5><0><7><8><9><10><0><0><13>

Answer 3

There does not seem to be a way to insert directly into an array. You can append elements to another array instead though:
result=()
for w in ${!array[#]}; do
result+=("${array[w]}")
comp=$(echo "${array[w+1]} - ${array[w]} " | bc)
if [ $comp = 1 ]; then
/* probably leave empty */
else
/* handle missing digits */
fi
done
As a final step, you can assign result back to the original array.