[hi-rachel] Week 06 Solutions

design-add-and-search-words-data-structure/hi-rachel.py

@@ -0,0 +1,38 @@
+class WordDictionary:
+
+    def __init__(self):
+        self.root = {"$": True}
+
+
+    # TC: O(W),  SC: O(W)
+    def addWord(self, word: str) -> None:
+        node = self.root
+        for ch in word:
+            if ch not in node:  # 글자가 node에 없으면
+                node[ch] = {"$": False}  # 아직 끝이 아님 표시
+            node = node[ch]  # 자식 노드로 변경
+        node["$"] = True  # 단어 끝 표시
+
+
+    # TC: O(26^W) => 최악의 경우 영어 알파벳 26개가 각 노드에서 다음 글자가 됨 * 글자수의 비례해서 호출 스택 깊어짐,  SC: O(W)
+    def search(self, word: str) -> bool:
+        def dfs(node, idx):
+            if idx == len(word):
+                return node["$"]
+
+            ch = word[idx]
+            if ch in node:
+                return dfs(node[ch], idx + 1)
+            if ch == ".":  # 글자가 .이라면
+                # 노드의 모든 자식 노드 호출 (어느 경로에서 글자가 일치할지 모르기 때문)
+                if any(dfs(node[k], idx + 1) for k in node if k != '$'): 
+                    return True
+            return False
+
+        return dfs(self.root, 0) # 최상위 노드, 최초 idx
+
+
+# Your WordDictionary object will be instantiated and called as such:
+# obj = WordDictionary()
+# obj.addWord(word)
+# param_2 = obj.search(word)

design-add-and-search-words-data-structure/hi-rachel.ts

@@ -0,0 +1,48 @@
+class WordDictionary {
+  root: Record<string, any>;
+
+  constructor() {
+    this.root = { $: true };
+  }
+
+  addWord(word: string): void {
+    let node = this.root;
+    for (const ch of word) {
+      if (!(ch in node)) {
+        node[ch] = { $: false };
+      }
+      node = node[ch];
+    }
+    node["$"] = true;
+  }
+
+  search(word: string): boolean {
+    const dfs = (node: Record<string, any>, idx: number): boolean => {
+      if (idx === word.length) return node["$"];
+
+      const ch = word[idx];
+      if (ch === ".") {
+        for (const key in node) {
+          if (key !== "$" && dfs(node[key], idx + 1)) {
+            return true;
+          }
+        }
+        return false;
+      }
+
+      if (ch in node) {
+        return dfs(node[ch], idx + 1);
+      }
+
+      return false;
+    };
+    return dfs(this.root, 0);
+  }
+}
+
+/**
+ * Your WordDictionary object will be instantiated and called as such:
+ * var obj = new WordDictionary()
+ * obj.addWord(word)
+ * var param_2 = obj.search(word)
+ */