Count how many times each word appears in a paragraph. A word is a maximal run of letters; compare words case-insensitively and report them in lower case. Print each distinct word and its count in alphabetical order, one per line as word count.
Use a TreeMap in Java and explain why it fits better than a HashMap here.
Constraints
- 1 ≤ total length ≤ 100000
- the text contains at least one letter
Input and output
- Input
- One or more lines of text.
- Output
- One line per distinct word: the word, a space and its count, in alphabetical order.
Examples
Input 1
The cat and the hat.
The ENDOutput
and 1
cat 1
end 1
hat 1
the 3"the" appears three times in different cases; the other words once each.
Input 2
Java, java; JAVA!Output
java 3All three are the same word: java 3.
Show hints
- Split on anything that is not a letter.
- TreeMap keeps keys sorted, so no separate sort step is needed.
Show the explanation
Split the text with the regular expression [^A-Za-z]+, lower-case each piece and call map.merge(word, 1, Integer::sum). A TreeMap is a red-black tree, so its keys come out in sorted order and each update is O(log d). A HashMap gives O(1) updates but iterates in no particular order, so you would need to sort the keys afterwards. Either is a fine answer if you can explain the trade-off.
Original UniCircle question. Last reviewed 22 Oct 2026.