NZEC Error in AWK programming - bash

Question

I am trying to solve the SPOJ problem SIZECON using the awk programming language.Using the below code
awk ' {
t = $1;
while ( t-- ) {
getline b;
x + b * (b > 0);
print x;
}
exit;
}'
OUTPUT:
4(No.of test cases)
5
5
-5
5
6
11
-1
11
The Expected INPUT and OUTPUT is:
Input:
4
5
-5
6
-1
Output:
11
the code works perfectly fine on my linux system and getting error when submitting in spoj (NZEC ERROR).Can anyone help me ?Thanks in Advance.

Answer 1

This might be what you want:
$ awk 'NR<2{t=$0;next} $0>0{s+=$0} NR>t{print s+0;exit}' file
11
I originally was just going to test for t having a value but the requirements on that site just say it will be less than 1000 so I guess it could be zero.
Also you need to print s+0 to ensure you get a numeric value instead of a null string if t is zero or the file is empty.
NR<2 tests for the first input line. It would be more naturally written as NR==1 but I understand you are looking for brevity over clarity.
awk scripts are made of a series of <condition> { <action> } segments, wrapped in an implicit while read loop so the posted script is equivalent to this pseudo-code in a procedural language:
while read line from file
do
lineNr++
if (lineNr < 2) {
t=$0
next
}
if (line > 0) {
s+=$0
}
if (lineNr > t) {
print s+0
exit
}
done
I think you should be able to figure the rest out given that and with google and the awk man pages when needed.

Answer 2

Given the set of integers, find the sum of all positive integers in it.
This is what you're doing? Seems pretty simple:
awk '
{
if ( NR == 1 ) {
total_to_read = $0 + 1
next
}
if ( $0 > 0 ) total += $0
if ( total_to_read == NR ) {
print total
exit
}
}' test.txt
The END phase is what you want to do at the end of the loop. I am simply taking each element in the loop and adding it to total if it's greater than 0.
It's not that simple. He needs to only read the number of values specified by the integer on the first line of input and he needs the briefest possible solution (excepting white space) - Ed Morton
My original answer was to show that you were overthinking Awk. Awk does the loop for you.
I've modified the above program to include the read the first number requirement. No more END needed. I save the first value, and go to the next line. When I get to the total lines to read, I print out that total, and do exit which should end my loop.
You can see this is actually equivalent to the psuedo-code given in Ed Morton's answer. It should be easier to understand.
Ed Morton pointed out that Awk can have a series of <expression> {code} segments. I always knew you could have one, but never thought of doing it multiple times.
This means that I could use this to imply if statements instead of spelling them out. Making your code a wee bit shorter:
awk '
( NR == 1 ) {
total_to_read = $1 + 1
next
}
( $0 > 0 ) {total += $0}
( total_to_read == NR ) {
print total
exit
}' test.txt
To make it even shorter, we could use shorter variable names. Let's use t for total_to_read and s for total:
awk '
( NR == 1 ) {
t = $1 + 1
next
}
( $0 > 0 ) {s += $0}
( t == NR ) {
print s
exit
}' test.txt
A few more tweaks. Instead of equals NR == 1, I'll do NR < 2. NR is the number of records, and if you are talking about NR being less than 2, it has to be 1. You can't have zero or negative number of records in your implied awk loop.
In my original program, I was adding 1 to t (total lines to read), then testing to exit if t == NR. If I don't add 1 to the total lines to read, I save a few characters, and I can test t > NR which saves another character:
awk '
( NR < 2 ) {
t = $0
next
}
( $0 > 0 ) {s += $0}
( t > NR ) {
print s
exit
}' test.txt
Now, let's eliminate all that useless whitespace and cram it all together!
awk 'NR<2{t=$0;next} $0>0{s+=$0} NR>t{print s+0;exit}' test.txt
And, I get Ed Morton's answer... Damn.
Well, at least I hope you understand this step-by-step explanation, and understand how Ed Morton's solution works.