feat : implement-trie-prefix-tree

Author: ekgns33

implement-trie-prefix-tree/ekgns33.java

@@ -0,0 +1,54 @@
+class Trie {
+
+  class Node {
+    boolean isEnd;
+    Node[] childs = new Node[26];
+    Node() {}
+  }
+
+  private Node root;
+
+  public Trie() {
+    this.root = new Node();
+  }
+
+  // O(m) when m is the length of word
+  public void insert(String word) {
+    Node curN = this.root;
+    for(char c : word.toCharArray()) {
+      if(curN.childs[c-'a'] == null) {
+        curN.childs[c-'a'] = new Node();
+      }
+      curN = curN.childs[c-'a'];
+    }
+    //end
+    curN.isEnd = true;
+  }
+  // O(k) when k is the length of searching word
+  public boolean search(String word) {
+    Node curN = this.root;
+    for(char c : word.toCharArray()) {
+      if(curN.childs[c-'a'] == null) return false;
+      curN = curN.childs[c-'a'];
+    }
+    return curN.isEnd;
+  }
+
+  // O(k) when k is the length of prefix
+  public boolean startsWith(String prefix) {
+    Node curN = this.root;
+    for(char c : prefix.toCharArray()) {
+      if(curN.childs[c-'a'] == null) return false;
+      curN = curN.childs[c-'a'];
+    }
+    return true;
+  }
+}
+
+/**
+ * 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);
+ */