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60 | class Trie {
public:
static constexpr int NODESIZE = 26;
bool isWord;
Trie* node[NODESIZE];
Trie() {
isWord = false;
for (int i = 0; i < NODESIZE; i++)
this->node[i] = nullptr;
}
void insert(string word) {
if (word.empty()) {
this->isWord = true;
return;
}
int idx = word[0] - 'a';
if (!this->node[idx])
this->node[idx] = new Trie();
this->node[idx]->insert(word.substr(1));
}
bool search(string word) {
if (word.empty())
return this->isWord;
int idx = word[0] - 'a';
if (!this->node[idx])
return false;
return this->node[idx]->search(word.substr(1));
}
bool startsWith(string prefix) {
if (prefix.empty())
return true;
int idx = prefix[0] - 'a';
if (!this->node[idx])
return false;
return this->node[idx]->startsWith(prefix.substr(1));
}
};
class Solution {
public:
bool wordBreak(string s, vector<string>& wordDict) {
int SIZE = s.size();
Trie trie;
for (string word : wordDict)
trie.insert(word);
vector<bool> dp(SIZE + 1, false);
dp[0] = true;
for (int i = 1; i <= SIZE; i++)
for (int j = 1; j <= i; j++)
if (dp[j - 1] && trie.search(s.substr(j - 1, i - j + 1)))
dp[i] = true;
return dp[SIZE];
}
};
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