feat: 297. Serialize and Deserialize Binary Tree

Author: gwbaik9717

serialize-and-deserialize-binary-tree/gwbaik9717.js

@@ -0,0 +1,132 @@
+// n: number of nodes, h: height of tree (max: n)
+// Time complexity: O(n)
+// Space complexity: O(2^h)
+
+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val) {
+ *     this.val = val;
+ *     this.left = this.right = null;
+ * }
+ */
+
+class _Queue {
+  constructor() {
+    this.q = [];
+    this.left = 0;
+    this.right = 0;
+  }
+
+  push(value) {
+    this.q.push(value);
+    this.right++;
+  }
+
+  shift() {
+    const rv = this.q[this.left];
+    delete this.q[this.left++];
+
+    return rv;
+  }
+
+  isEmpty() {
+    return this.left === this.right;
+  }
+}
+
+const isValid = (data) => {
+  if (data === undefined || data === null) {
+    return false;
+  }
+
+  return true;
+};
+
+/**
+ * Encodes a tree to a single string.
+ *
+ * @param {TreeNode} root
+ * @return {string}
+ */
+var serialize = function (root) {
+  const answer = [null];
+
+  const bfs = (current) => {
+    const q = new _Queue();
+    q.push([1, current]);
+
+    while (!q.isEmpty()) {
+      const [i, current] = q.shift();
+
+      if (current === null) {
+        answer[i] = current;
+        continue;
+      }
+
+      answer[i] = current.val;
+
+      const left = 2 * i;
+      const right = left + 1;
+
+      if (current.left) {
+        q.push([left, current.left]);
+      } else {
+        q.push([left, null]);
+      }
+
+      if (current.right) {
+        q.push([right, current.right]);
+      } else {
+        q.push([right, null]);
+      }
+    }
+  };
+
+  bfs(root);
+
+  while (answer.length > 1 && !isValid(answer.at(-1))) {
+    answer.pop();
+  }
+
+  return answer;
+};
+
+/**
+ * Decodes your encoded data to tree.
+ *
+ * @param {string} data
+ * @return {TreeNode}
+ */
+var deserialize = function (data) {
+  if (data.length === 1) {
+    return null;
+  }
+
+  const root = new TreeNode(data[1]);
+  const q = new _Queue();
+  q.push([1, root]);
+
+  while (!q.isEmpty()) {
+    const [i, current] = q.shift();
+
+    const left = i * 2;
+    const right = left + 1;
+
+    if (left <= data.length && isValid(data[left])) {
+      current.left = new TreeNode(data[left]);
+      q.push([left, current.left]);
+    }
+
+    if (right <= data.length && isValid(data[right])) {
+      current.right = new TreeNode(data[right]);
+      q.push([right, current.right]);
+    }
+  }
+
+  return root;
+};
+
+/**
+ * Your functions will be called as such:
+ * deserialize(serialize(root));
+ */