I need help to find all combinations (sum) of array elements in bash. here is an excerpt from the code:
#!/bin/bash
array=("31" "-41" "59" "26" "-53" "58" "97" "-93" "-23" "84") # min 1 vlaue
arrLength=("${#array[@]}")
for (( i=0; i < $arrLength; i++))
do
#echo "$i"
for (( j=$i; j > 0; j-- ))
do
summ=$(( array[j] ))
bak=$((array[0] + summ))
echo "$summ ; $bak"
done
echo "_____________________________"
done
This finds the single pairs and the double pairs. What is missing are the three-pairs (eg 31+(-41)+59), the combinations of four...and so on. I don't want to hard code it, because the number of elements can change in my program.
For help I would be very grateful. Thank you.
As commented by others, we have 1023 combinations for 10 numbers, excluding the empty set. These combinations can be associated with the bit pattern between 0000000001
and 1111111111
. Then would you please try:
#!/bin/bash
array=("31" "-41" "59" "26" "-53" "58" "97" "-93" "-23" "84")
n=${#array[@]} # number of elements
for (( i = 1; i < (1 << n); i++ )); do # loop between 1 and 1023
sum=0; list=() # initialize variables
for (( j = 0; j < n; j++ )); do # loop over the bit slice position
if (( (1 << j) & i )); then # if the bit is set
(( sum += ${array[j]} )) # then pick the element to sum
list+=("${array[j]}") # append to an array to report
fi
done
(IFS=,; printf "(%s) = %d\n" "${list[*]}" "$sum")
# report the sum of the set
done
First few lines of the output:
(31) = 31
(-41) = -41
(31,-41) = -10
(59) = 59
(31,59) = 90
(-41,59) = 18
(31,-41,59) = 49
<snip>
It will print 1023 lines in total.
One awk
idea using a recursive function:
array=("31" "-41" "59" "26" "-53" "58" "97" "-93" "-23" "84")
printf "%s\n" "${array[@]}" |
awk '
function find_sum(i, sum, label, j) {
printf "%8s = %s\n",sum,label
for (j=i+1;j<=FNR;j++)
find_sum(j, sum+item[j], label " + " item[j])
}
{ item[FNR]=$1 }
END { for (i=1;i<=FNR;i++)
find_sum(i, item[i], item[i])
}
'
NOTE: since we perform all operations with a single awk
call we can reduce the total run time from ~13 seconds ( bash
looping construct) to ~0.1 second ( awk
)
This generates:
31 = 31
-10 = 31 + -41
49 = 31 + -41 + 59
75 = 31 + -41 + 59 + 26
22 = 31 + -41 + 59 + 26 + -53
80 = 31 + -41 + 59 + 26 + -53 + 58
177 = 31 + -41 + 59 + 26 + -53 + 58 + 97
84 = 31 + -41 + 59 + 26 + -53 + 58 + 97 + -93
61 = 31 + -41 + 59 + 26 + -53 + 58 + 97 + -93 + -23
145 = 31 + -41 + 59 + 26 + -53 + 58 + 97 + -93 + -23 + 84
168 = 31 + -41 + 59 + 26 + -53 + 58 + 97 + -93 + 84
154 = 31 + -41 + 59 + 26 + -53 + 58 + 97 + -23
238 = 31 + -41 + 59 + 26 + -53 + 58 + 97 + -23 + 84
261 = 31 + -41 + 59 + 26 + -53 + 58 + 97 + 84
-13 = 31 + -41 + 59 + 26 + -53 + 58 + -93
... snip ...
35 = 58 + -23
119 = 58 + -23 + 84
142 = 58 + 84
97 = 97
4 = 97 + -93
-19 = 97 + -93 + -23
65 = 97 + -93 + -23 + 84
88 = 97 + -93 + 84
74 = 97 + -23
158 = 97 + -23 + 84
181 = 97 + 84
-93 = -93
-116 = -93 + -23
-32 = -93 + -23 + 84
-9 = -93 + 84
-23 = -23
61 = -23 + 84
84 = 84
If your memory can hold it, double the array with each new item by replicating it with the new item added. This solution relies on including the empty set (with sum 0
) for initializiation. To exclude it, strip it off at the end.
a=(31 -41 59 26 -53 58 97 -93 -23 84)
b=(0)
for i in ${a[@]}; do for j in ${b[@]}; do b+=( $((i+j)) ); done; done
$ echo ${#b[@]}
1024
$ printf '%s\n' ${b[@]}
0
31
-41
-10
59
:
:
86
155
186
114
145
The same approach including the steps of calculation:
a=(31 -41 59 26 -53 58 97 -93 -23 84)
b=("0 = 0")
for i in ${a[@]}; do for j in "${b[@]}"; do b+=("${j%=*}+ $i = $((i+${j#*=}))"); done; done
$ echo ${#b[@]}
1024
$ printf '%s\n' "${b[@]}"
0 = 0
0 + 31 = 31
0 + -41 = -41
0 + 31 + -41 = -10
0 + 59 = 59
:
:
0 + 31 + -41 + 26 + -53 + 58 + 97 + -93 + -23 + 84 = 86
0 + 59 + 26 + -53 + 58 + 97 + -93 + -23 + 84 = 155
0 + 31 + 59 + 26 + -53 + 58 + 97 + -93 + -23 + 84 = 186
0 + -41 + 59 + 26 + -53 + 58 + 97 + -93 + -23 + 84 = 114
0 + 31 + -41 + 59 + 26 + -53 + 58 + 97 + -93 + -23 + 84 = 145
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.