题目
- 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.
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
注意点
Note:
- Don't worry about handling ties, it is guaranteed that each word's frequency count is unique.
- Could you write it in one-line using Unix pipes?
解法１
# Read from the file words.txt and output the word frequency list to stdout.
cat words.txt | awk -F ' ' '{ for(i=1; i<=NF; i++) print $i }' | sort | uniq -c | sort -n -r | awk -F ' ' '{ print $2, $1}'
The variable NF is set to the total number of fields in the input record.
解法２
cat words.txt | tr -s ' ' '\n' | sort | uniq -c | sort -n -r | awk '{ print $2, $1 }'
-
tr -s ' ' '\n': 将多个' '替换为单个\n
tr - translate or delete characters
-s, --squeeze-repeats replace each sequence of a repeated character that is listed in the last specified SET, with a single occurrence of that character
解法３：与解法２对比
cat words.txt | sed 's/\s/\n/g' | sort | uniq -c | sort -n -r | awk '{ if($2 != "") print $2, $1 }'
-
sed 's/ /\n/g': 将单个' '替换为单个\n - 如果有多个
' '也就会生成多个'\n',但是我们只需要一个。 - 同时多生成的
'\n'也会被计数。 -
if($2 != "")：我们在awk输出的时候对空行(换行符)进行检查。
解法４
awk '{ for (i=1; i<=NF; i++) { ++D[$i]; } } END { for (i in D) { print i, D[i] } }' words.txt | sort -n -r -k 2
引用和推荐阅读:
https://leetcode.com/problems/word-frequency/
https://unix.stackexchange.com/a/378550/323210
https://leetcode.com/problems/word-frequency/discuss/55443/My-simple-solution-(one-line-with-pipe)
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