feat: solve implement trie prefix tree

Author: GangBean

implement-trie-prefix-tree/GangBean.java

@@ -0,0 +1,52 @@
+class Trie {
+    /**
+    1. understanding
+    - Trie data structure
+    - To process at most 3 * 10^4 calls in proper time, each call must be under O(N), where N is the length of word.
+    - insert: insert data into Trie
+    - search: find data from inserted Datas
+    - startsWith: find
+    2. strategy
+    - a) use list to save inserted words
+        - insert: O(1)
+        - search: O(L * N), where L is the length of list, N is the length of each words.
+        - startsWith: O(L * N)
+        - total call to be 3 * 10^4, i assume each method call count at most 10^4 or linear correlation in 10^4 scale.
+        - so, L <= 10^4, N <= 10^4
+        - space: O(L * N)
+        - it is enough to pass, but there are duplicates in space and also in excution count.
+    - b) 
+    */
+
+    private List<String> words;
+    public Trie() {
+        words = new ArrayList<>();
+    }
+    
+    public void insert(String word) {
+        words.add(word);
+    }
+    
+    public boolean search(String word) {
+        for (String w: words) {
+            if (w.equals(word)) return true;
+        }
+        return false;
+    }
+    
+    public boolean startsWith(String prefix) {
+        for (String w: words) {
+            if (w.indexOf(prefix) == 0) return true;
+        }
+        return false;
+    }
+}
+
+/**
+ * Your Trie object will be instantiated and called as such:
+ * Trie obj = new Trie();
+ * obj.insert(word);
+ * boolean param_2 = obj.search(word);
+ * boolean param_3 = obj.startsWith(prefix);
+ */
+