LC 648. Replace Words

In English, we have a concept called root, which can be followed by some other words to form another longer word - let's call this word successor. For example, the root an, followed by other, which can form another word another.

Now, given a dictionary consisting of many roots and a sentence. You need to replace all the successor in the sentence with the root forming it. If a successor has many roots can form it, replace it with the root with the shortest length.

You need to output the sentence after the replacement.

Example 1:

Input: dict = ["cat", "bat", "rat"]
sentence = "the cattle was rattled by the battery"
Output: "the cat was rat by the bat"

Note:

1. The input will only have lower-case letters.
2. 1 <= dict words number <= 1000
3. 1 <= sentence words number <= 1000
4. 1 <= root length <= 100
5. 1 <= sentence words length <= 1000

Runtime: 64 ms, faster than 45.77% of C++ online submissions for Replace Words.

#include <vector>
#include <string>
using namespace std;

class TrieNode{
public:
  string word;
  TrieNode* children[];
  TrieNode(){
    for(int i=; i<; i++) children[i] = nullptr;
    word = "";
  }
};
class Trie{
public:
  TrieNode* root;
  Trie() {
    root = new TrieNode();
  }
  void buildtrie(vector<string>& words){
    for(int i=; i<words.size(); i++){
      TrieNode* tmp = root;
      for(int j=; j<words[i].size(); j++){
        int idx = words[i][j] - 'a';
        if(!tmp->children[idx]) tmp->children[idx] = new TrieNode();
        tmp = tmp->children[idx];
      }
      tmp->word = words[i];
    }
  }

  string hasprefix(string word){
    TrieNode* tmp = root;
    string prefix = "";
    //cout << word << endl;
    for(int i=; i<word.size(); i++){
      int idx = word[i] - 'a';
      //cout << word << " " << idx << endl;
      if(!tmp->children[idx]) return prefix;
      tmp = tmp->children[idx];
      if(tmp->word != ""){
        //cout << prefix << endl;
        prefix = tmp->word;
        break;
      }
    }
    return prefix;
  }

};

class Solution {
public:
  string replaceWords(vector<string>& dict, string sentence) {
    Trie trie = Trie();
    trie.buildtrie(dict);
    vector<int> spaceidx;
    for(int i=; i<sentence.size(); i++){
      if(sentence[i] == ' ') spaceidx.push_back(i);
    }
    vector<string> sent_vec;
    int idx = ;
    if(spaceidx.size() == ){
      sent_vec.push_back(sentence);
    }else{
      for(int i=; i<spaceidx.size(); i++){
        sent_vec.push_back(sentence.substr(idx, spaceidx[i] - idx));
        idx = spaceidx[i] + ;
      }
    }
    //for(auto x : spaceidx) cout << x << endl;
    sent_vec.push_back(sentence.substr(idx));
    //cout << sent_vec.size() << endl;
    //for(auto s : sent_vec) cout << s << endl;
    vector<string> retvec;

    for(int i=; i<sent_vec.size(); i++){
      string tmpstr = trie.hasprefix(sent_vec[i]);
      //cout << sent_vec[i] << endl;
      if(tmpstr == "") retvec.push_back(sent_vec[i]);
      else retvec.push_back(tmpstr);
    }
    string ret = "";
    for(auto s : retvec) ret += s + " ";
    return ret.substr(,ret.size()-);
  }
};