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LeetCode one-liner bash script problems and answers


Word Frequency

Write a bash script to calculate the frequency of each word in a text file words.txt.

For simplicity sake, you may assume:

  • words.txt contains only lowercase characters and space ’ ’ characters.
  • Each word must consist of lowercase characters only.
  • Words are separated by one or more whitespace characters.

Assume that words.txt has the following content:

the day is sunny the the
the sunny is is

Your script should output the following, sorted by descending frequency:

the 4
is 3
sunny 2
day 1


egrep -o "\b[[:alpha:]]+\b" words.txt |sort -n |uniq -c |sort -k1nr |awk '{print $2, $1}'

Valid Phone Numbers

Given a text file file.txt that contains a list of phone numbers (one per line), write a one-liner bash script to print all valid phone numbers.

You may assume that a valid phone number must appear in one of the following two formats: (xxx) xxx-xxxx or xxx-xxx-xxxx. (x means a digit)

You may also assume each line in the text file must not contain leading or trailing white spaces.

Assume that file.txt has the following content:

123 456 7890
(123) 456-7890

Your script should output the following valid phone numbers:

(123) 456-7890


grep -E '^([0-9]{3}-|\([0-9]{3}\) )[0-9]{3}-[0-9]{4}$' file.txt

Transpose File

Given a text file file.txt, transpose its content.

You may assume that each row has the same number of columns, and each field is separated by the ’ ’ character.

If file.txt has the following content:

name age
alice 21
ryan 30

Output the following:

name alice ryan
age 21 30


for x in $(seq 1 $(awk 'END{if (NR>NF) print NF;else print NF}' file.txt));do A=$(cat file.txt|cut -d ' ' -f $x|while read L;do echo -n "$L ";done);echo ${A% };done

Tenth Line

Given a text file file.txt, print just the 10th line of the file.

Assume that file.txt has the following content:

Line 1
Line 2
Line 3
Line 4
Line 5
Line 6
Line 7
Line 8
Line 9
Line 10

Your script should output the tenth line, which is:

Line 10


sed -n '10p' file.txt
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