Selecting first nth rows by groups using AWK - awk

Question

I have the following file with 4 fields. There are 3 groups in field 2, and the 4th field consists 0's and 1's.
The first field is just the index.
I like to use AWK to do the following task
Select the first 3 rows of group 1 (Note that group 1 has only 2 rows). The number of rows is based on the number of 1's found in the 4th field times 3.
Select the first 6 rows of group 2. The number of rows is based on the number of 1's found in the 4th field times 3.
Select the first 9 rows of group 3. The number of rows is based on the number of 1's found in the 4th field times 3.
So 17 rows are selected for the output file.
Thank you for your help.
Input
1 1 TN1148 1
2 1 S52689 0
3 2 TA2081 1
4 2 TA2592 1
5 2 TA4011 0
6 2 TA4246 0
7 2 TA4275 0
8 2 TB0159 0
9 2 TB0392 0
10 3 TB0454 1
11 3 TB0496 1
12 3 TB1181 1
13 3 TC0027 0
14 3 TC1340 0
15 3 TC2247 0
16 3 TC3094 0
17 3 TD0106 0
18 3 TD1146 0
19 3 TD1796 0
20 3 TD3587 0
Output
1 1 TN1148 1
2 1 S52689 0
3 2 TA2081 1
4 2 TA2592 1
5 2 TA4011 0
6 2 TA4246 0
7 2 TA4275 0
8 2 TB0159 0
10 3 TB0454 1
11 3 TB0496 1
12 3 TB1181 1
13 3 TC0027 0
14 3 TC1340 0
15 3 TC2247 0
16 3 TC3094 0
17 3 TD0106 0
18 3 TD1146 0

Answer 1

The key to this awk program is to pass the input file in twice: Once to count how many rows you want and once to print them.
awk '
NR == FNR {wanted_rows[$2] += 3*$4; next}
--wanted_rows[$2] >= 0 {print}
' input_file.txt input_file.txt

Answer 2

#!/usr/bin/awk -f
# by Dennis Williamson - 2010-12-02
# for http://stackoverflow.com/questions/4334167/selecting-first-nth-rows-by-groups-using-awk
$2 == prev {
count += $4
groupcount++
array[idx++] = $0
}
$2 != prev {
if (NR > 1) {
for (i=0; i<count*3; i++) {
if (i == groupcount) break
print array[i]
}
}
prev = $2
count = 1
groupcount = 1
split("", array) # delete the array
idx = 0
array[idx++] = $0
}
END {
for (i=0; i<count*3; i++) {
if (i == groupcount) break
print array[i]
}
}