LeetCode Shell Problems
2015-04-11 19:58
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195. Tenth Line -- 第十行
How would you print just the 10th line of a file?
Solution:
awk 'NR==10' file.txt
194. Transpose File -- 转置文件
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.
For example, if file.txt has the following content:**
name age
alice 21
ryan 30
Output the following:**
name alice ryan
age 21 30
Solution:
awk '{
max_nf = NF
max_nr = NR
for (x = 1; x <= NF; x++) {
vector[x, NR] = $x
}
}
END {
for (x = 1; x <= max_nf; x++) {
for (y = 1; y <= max_nr; y++) {
printf("%s", vector[x, y])
if (y < max_nr)
printf(" ")
}
if (x < max_nf)
printf("\n")
}
}' file.txt193. Valid Phone Numbers -- 有效电话号码
Given a text file file.txt that contains list of phone numbers (one per line), write a one liner bash script to print all valid phone numbers.
You may assume that a valid phone number must appear in one of the following two formats: (xxx) xxx-xxxx or xxx-xxx-xxxx. (x means a digit)
You may also assume each line in the text file must not contain leading or trailing white spaces.
**For example, assume that file.txt has the following content:**
987-123-4567
123 456 7890
(123) 456-7890
Your script should output the following valid phone numbers:
987-123-4567
(123) 456-7890
Solution:
awk '/^[0-9]{3}-[0-9]{3}-[0-9]{4}$/ || /^\([0-9]{3}\) [0-9]{3}-[0-9]{4}$/' file.txt192. Word Frequency -- 词频
Write a bash script to calculate the frequency of each word in a text file words.txt.
For simplicity sake, you may assume:
words.txt contains only lowercase characters and space ' ' characters.
Each word must consist of lowercase characters only.
Words are separated by one or more whitespace characters.
For example, assume that words.txt has the following content:**
the day is sunny the the
the sunny is is
Your script should output the following, sorted by descending frequency:
the 4
is 3
sunny 2
day 1
Note:**
Don't worry about handling ties, it is guaranteed that each word's frequency count is unique.
Solution:
awk '{for(i=1;i<=NF;i++) a[$i]+=1} END{for(i in a) print i,a[i] | "sort -r -n -k2"}' words.txt
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