How to split a string into words. Ex: “stringintowords” -> “String Into Words”?

Question

What is the right way to split a string into words ? (string doesn\'t contain any spaces or punctuation marks)

For example: \"stringintowords\" -> \"String Into Word

Answer 1

A simple Java solution which has O(n^2) running time.

public class Solution {
    // should contain the list of all words, or you can use any other data structure (e.g. a Trie)
    private HashSet dictionary;

    public String parse(String s) {
        return parse(s, new HashMap());
    }

    public String parse(String s, HashMap map) {
        if (map.containsKey(s)) {
            return map.get(s);
        }
        if (dictionary.contains(s)) {
            return s;
        }
        for (int left = 1; left < s.length(); left++) {
            String leftSub = s.substring(0, left);
            if (!dictionary.contains(leftSub)) {
                continue;
            }
            String rightSub = s.substring(left);
            String rightParsed = parse(rightSub, map);
            if (rightParsed != null) {
                String parsed = leftSub + " " + rightParsed;
                map.put(s, parsed);
                return parsed;
            }
        }
        map.put(s, null);
        return null;
    }
}