leetcode.140. Word Break II

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Given a string s and a dictionary of words dict, add spaces in s to construct a sentence where each word is a valid dictionary word.

Return all such possible sentences.

For example, given
s = "catsanddog",
dict = ["cat", "cats", "and", "sand", "dog"].

A solution is ["cats and dog", "cat sand dog"].

 class Solution { public:      void breakWord(vector<string> &res, string &s, unordered_set<string> &dict, string str, int idx, vector<bool> &dp) {          string substr;          for (int len = 1; idx + len < s.length() + 1; ++len) {             if (dp[idx + len] && dict.count(s.substr(idx,len)) > 0) {                 substr = s.substr(idx, len);                 if (idx + len < s.length()) {                     breakWord(res, s, dict, str + substr + " ", idx + len, dp);                 } else {                     res.push_back(str + substr);                     return;                 }             }         }     }          vector<string> wordBreak(string s, unordered_set<string> &dict) {         vector<bool> dp(s.length() + 1, false);         dp[0] = true;         for (int i = 0; i < s.length(); ++i) {             if (dp[i]) {                 for (int len = 1; i + len < s.length() + 1; ++len) {                     if (dict.count(s.substr(i, len)) > 0) {                         dp[i + len] = true;                     }                 }             }         }         vector<string> res;         if (dp[s.length()])              breakWord(res, s, dict, "", 0, dp);         return res;     } };

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