feat(soobing): week12 > serialize-and-deserialize-binary-tree

Author: soobing

serialize-and-deserialize-binary-tree/soobing.ts

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+/**
+ * 문제 설명
+ * - 이진 트리를 직렬화/역직렬화 하는 문제
+ *
+ * 아이디어
+ * 1) 트리를 순회하면서 value값만 담는다.
+ *  - DFS, BFS 둘 다 가능
+ *  - DFS는 재귀 기반이라 코드가 간결하고, BFS 보다 메모리 사용량은 적지만, 깊은 트리에서는 스택 오버플로우가 발생할 수 있다.
+ *  - 반면에 BFS는 큐를 많이 사용해서 폭이 넓은 트리에서 비효율적일 수 있지만,
+ */
+
+class TreeNode {
+  val: number;
+  left: TreeNode | null;
+  right: TreeNode | null;
+  constructor(val?: number, left?: TreeNode | null, right?: TreeNode | null) {
+    this.val = val === undefined ? 0 : val;
+    this.left = left === undefined ? null : left;
+    this.right = right === undefined ? null : right;
+  }
+}
+
+/*
+ * Encodes a tree to a single string.
+ */
+function serialize(root: TreeNode | null): string {
+  const result: string[] = [];
+
+  const dfs = (node: TreeNode | null) => {
+    if (node === null) {
+      result.push("null");
+      return;
+    }
+
+    result.push(node.val.toString());
+    dfs(node.left);
+    dfs(node.right);
+  };
+
+  dfs(root);
+  return result.join(",");
+}
+
+/*
+ * Decodes your encoded data to tree.
+ */
+function deserialize(data: string): TreeNode | null {
+  const values = data.split(",");
+  let i = 0;
+  const dfs = () => {
+    if (values[i] === "null") {
+      i++;
+      return null;
+    }
+
+    const node = new TreeNode(Number(values[i]));
+    i++;
+    node.left = dfs();
+    node.right = dfs();
+    return node;
+  };
+  return dfs();
+}
+
+/**
+ * Your functions will be called as such:
+ * deserialize(serialize(root));
+ */
+
+/*
+ * Encodes a tree to a single string.
+ */
+function serializeBFS(root: TreeNode | null): string {
+  if (!root) return "null";
+
+  const queue: (TreeNode | null)[] = [root];
+  const result: string[] = [];
+
+  while (queue.length > 0) {
+    const node = queue.shift();
+    if (node) {
+      result.push(node.val.toString());
+      queue.push(node.left);
+      queue.push(node.right);
+    } else {
+      result.push("null");
+    }
+  }
+  return result.join(",");
+}
+
+/*
+ * Decodes your encoded data to tree.
+ */
+function deserializeBFS(data: string): TreeNode | null {
+  const values = data.split(",");
+
+  if (values[0] === "null") return null;
+
+  const root = new TreeNode(Number(values[0]));
+  let i = 1;
+  const queue: (TreeNode | null)[] = [root];
+
+  while (queue.length > 0 && i < values.length) {
+    const current = queue.shift();
+    const left = values[i++];
+    const right = values[i++];
+
+    if (left !== "null") {
+      current!.left = new TreeNode(Number(left));
+      queue.push(current!.left);
+    }
+
+    if (right !== "null") {
+      current!.right = new TreeNode(Number(right));
+      queue.push(current!.right);
+    }
+  }
+  return root;
+}
+
+/**
+ * Your functions will be called as such:
+ * deserialize(serialize(root));
+ */