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Author: hajin-kim

0297-serialize-and-deserialize-binary-tree/0297-serialize-and-deserialize-binary-tree.kt

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+import java.util.ArrayDeque
+import java.util.LinkedList
+import java.util.Queue
+
+/**
+ * Definition for a binary tree node.
+ * class TreeNode(var `val`: Int) {
+ *     var left: TreeNode? = null
+ *     var right: TreeNode? = null
+ * }
+ */
+
+class Codec {
+    // Encodes a URL to a shortened URL.
+    fun serialize(root: TreeNode?): String {
+        if (root == null)
+            return "[]"
+
+        val result = mutableListOf<Int?>()
+
+        val queue: Queue<TreeNode?> = LinkedList()
+        queue += root
+
+        var nonNullCount = 1
+        while (queue.isNotEmpty() && nonNullCount > 0) {
+            nonNullCount = 0
+            repeat(queue.size) {
+                val now = queue.poll()
+
+                result += now?.`val`
+
+                if (now == null) {
+                    return@repeat
+                }
+
+                for (child in arrayOf(now.left, now.right)) {
+                    queue.add(child)
+                    if (child != null)
+                        nonNullCount += 1
+                }
+            }
+        }
+
+        return result.joinToString(",", "[", "]")
+    }
+
+    // Decodes your encoded data to tree.
+    fun deserialize(data: String): TreeNode? {
+        if (data == "[]")
+            return null
+
+        val dataList = data.slice(1 until data.lastIndex)
+            .split(',')
+            .map { it.toIntOrNull() }
+
+        var pointer = 0
+        val root = TreeNode(dataList[pointer++]!!)
+
+        val queue: Queue<TreeNode> = ArrayDeque()
+        queue += root
+
+        while (queue.isNotEmpty() && pointer < dataList.size) {
+            val now = queue.poll()
+
+            val leftVal = dataList[pointer++]
+            val rightVal = dataList[pointer++]
+
+            if (leftVal != null) {
+                val left = TreeNode(leftVal)
+                now.left = left
+                queue += left
+            }
+
+            if (rightVal != null) {
+                val right = TreeNode(rightVal)
+                now.right = right
+                queue += right
+            }
+        }
+
+        return root
+    }
+}
+
+/**
+ * Your Codec object will be instantiated and called as such:
+ * var ser = Codec()
+ * var deser = Codec()
+ * var data = ser.serialize(longUrl)
+ * var ans = deser.deserialize(data)
+ */