leetcode 192. Word Frequency

題目： 192. Word Frequency

解答：

tr -s: truncate（縮短） the string with target string, but only remaining one instance (e.g. multiple whitespaces)

把多個連續的空格縮短為一個空格，即隻保留一個空格， 然後用’\n’替換空格。

cat words.txt | tr -s ' ' 多個連續的空格縮短為一個
cat words.txt | tr -s ' ' '*' 縮短後的一個空格被 ‘*’替換
uniqu -c 
           

sort: To make the same string successive so that uniq could count the same string fully and correctly.

uniq -c: uniq is used to filter out the repeated lines which are successive, -c means counting

sort -r: -r means sorting in descending order

awk ‘{ print 2, 1 }’: To format the output, see here.

練習：

cat testfile
           

world

boy

hello

zero

zero

zero

alive

alive

先排序再去重，結果如下。

alive

boy

hello

world

zero

先排序再計數，結果如下

2 alive

1 boy

1 hello

1 world

3 zero