Create trie.cpp

Data Structure/trie.cpp

@@ -0,0 +1,79 @@
+struct Trie{
+	const int A = 26;
+	int N;
+
+	vector<vector<int> > next;
+	vector<int> cnt;
+
+	Trie() : N(0) {
+		node();
+	}
+
+	int node(){
+		next.emplace_back(A, -1);
+		cnt.emplace_back(0);
+
+		return N++;
+	}
+
+	inline int get(char c){
+		return c-'a';
+	}
+
+	inline void insert(string s){
+		int cur = 0;
+		for(char c : s){
+			int to = get(c);
+			if(next[cur][to] == -1) next[cur][to] = node();
+			cur = next[cur][to];
+		}
+		cnt[cur]++;
+	}
+
+	inline bool find(string s){
+		int cur = 0;
+		for(char c : s){
+			int to = get(c);
+			if(next[cur][to] == -1) return false;
+			cur = next[cur][to];
+		}
+		return cnt[cur]!=0;
+	}
+
+	// Doesn't check for existance
+	inline void erase(string s){
+		int cur = 0;
+		for(char c : s){
+			int to =get(c);
+			cur = next[cur][to];
+		}
+		cnt[cur]--;
+	}
+
+	vector<string> dfs(){
+		stack<pair<int, int> > st;
+		string s;
+		vector<string> ret;
+
+		for(st.push({0, -1}), s.push_back('$'); !st.empty(); ){
+			auto [u,  c] = st.top();
+			st.pop();
+			s.pop_back();
+			c++;
+
+			if(c <  A){
+				st.push({u, c});
+				s.push_back(c+'a');
+				int v = next[u][c];
+
+				if(~v){
+					if(cnt[v]) ret.emplace_back(s);
+					st.push({v, -1});
+					s.push_back('$');
+				}
+			}
+		}
+
+		return ret;
+	}
+};