Given a non-empty string s and a dictionary wordDict containing a list of non-empty words, add spaces in s to construct a sentence where each word is a valid dictionary word. Return all such possible sentences.

Word Break II

Solution1

Recursive

public ArrayList<String> wordBreak(String s, List<String> dict) {
    Map<String, ArrayList<String>> memo = new HashMap<>();
    return wordBreakHelper(s, dict, memo);
}

public ArrayList<String> wordBreakHelper(String s, List<String> dict, Map<String, ArrayList<String>> memo) {
    if (memo.containsKey(s)) {
        return memo.get(s);
    }

    ArrayList<String> result = new ArrayList<>();
    if (s.length() == 0) {
        return result;
    }

    if (dict.contains(s)) {
        result.add(s);
    }

    for (int length = 1; length < s.length(); length++) {
        String word = s.substring(0, length);
        if (!dict.contains(word)) {
            continue;
        }

        String suffix = s.substring(length);
        List<String> segmentations = wordBreakHelper(suffix, dict, memo);
        for (String segmentation : segmentations) {
            result.add(word + " " + segmentation);
        }
    }
    memo.put(s, result);
    return result;
}