Create index.kt

Author: masx200

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

@@ -0,0 +1,73 @@
+package masx200.leetcode_test.serialize_and_deserialize_binary_tree
+
+import masx200.leetcode_test.insert_into_a_binary_search_tree.TreeNode
+
+class Codec {
+
+    fun serialize(root: TreeNode?): String {
+        fun serialize(node: Any?): String {
+            return when (node) {
+                null -> "null"
+                is TreeNode -> {
+                    listOf(node.`val`, node.left, node.right).joinToString(",", "[", "]") { element
+                        ->
+                        serialize(element)
+                    }
+                }
+                else -> node.toString()
+            }
+        }
+        return serialize(root)
+    }
+
+    fun deserialize(data: String): TreeNode? {
+
+        var i = 0
+        fun dfs(): TreeNode? {
+            val node = TreeNode()
+            val children = mutableListOf<TreeNode?>()
+            var sign = 1
+            while (i < data.length) {
+
+                if (data[i] == ',') i++
+                else if (data[i] == '-') {
+                    sign = -1
+                    i++
+                } else if (data[i].isDigit()) {
+                    var next = i - 1
+                    var j = i
+                    while (j < data.length) {
+                        if (!data[j].isDigit()) {
+                            next = j
+                            break
+                        }
+                        j++
+                    }
+
+                    node.`val` = data.substring(i, next).toInt() * sign
+                    i = next
+                    sign = 1
+                } else if (data[i] == '[') {
+                    i++
+                    children.add(dfs())
+                } else if (data[i] == ']') {
+                    i++
+                    children.forEachIndexed { index, tree ->
+                        if (index == 0) node.left = tree else if (index == 1) node.right = tree
+                    }
+
+                    return node
+                } else if (data.substring(i, i + 4) == "null") {
+                    i += 4
+                    children.add(null)
+                }
+            }
+
+            return children[0]
+        }
+        return when (data) {
+            "null" -> null
+            else -> dfs()
+        }
+    }
+}