Leetcode 140 Solution

This article provides solution to leetcode question 140 (word-break-ii)
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https://leetcode.com/problems/word-break-ii

Solution

class Solution {
    vector<vector<string>> cache;
    vector<bool> cached;
    vector<string> res;
public:
    vector<string> wordBreak(const string& s, int i, unordered_set<string>& wordSet)
    {
        vector<string> res;

        if (i == s.size())
        {
            res.push_back("");
            return res;
        }

        if (cached[i])
            return cache[i];

        for (int j = i; j < s.size(); j++)
        {
            string substr = s.substr(i, j - i + 1);

            if (wordSet.find(substr) == wordSet.end())
                continue;

            auto rest_strs = wordBreak(s, j + 1, wordSet);

            for (auto rest_str : rest_strs)
                res.push_back(rest_str.empty() ? substr : substr + " " + rest_str);
        }

        cached[i] = true;
        return cache[i] = res;
    }

    vector<string> wordBreak(string s, vector<string>& wordDict) {
        cache.resize(s.size());
        cached.resize(s.size());

        unordered_set<string> wordSet;

        for (auto word : wordDict)
            wordSet.insert(word);

        return wordBreak(s, 0, wordSet);
    }
};