Add kotlin code for the utils file (#1175)

* feat(kotlin): add kotlin code for utils file.

* Update ListNode.kt

* Update PrintUtil.kt

---------

Co-authored-by: Yudong Jin <krahets@163.com>

codes/kotlin/utils/ListNode.kt

@@ -0,0 +1,34 @@
+/**
+ * File: ListNode.kt
+ * Created Time: 2024-01-25
+ * Author: curtishd (1023632660@qq.com)
+ */
+
+package utils
+
+/* 链表节点 */
+class ListNode(var value: Int) {
+    var next: ListNode? = null
+
+    companion object {
+        /* 将列表序列化为链表 */
+        fun arrToLinkedList(arr: IntArray): ListNode? {
+            val dum = ListNode(0)
+            var head = dum
+            for (value in arr) {
+                head.next = ListNode(value)
+                head = head.next!!
+            }
+            return dum.next
+        }
+
+        /* 获取链表中值为 value 的节点 */
+        fun getListNode(h: ListNode, value: Int): ListNode {
+            var head = h
+            while (head.value != value) {
+                head = head.next!!
+            }
+            return head
+        }
+    }
+}

codes/kotlin/utils/PrintUtil.kt

@@ -0,0 +1,106 @@
+/**
+ * File: PrintUtil.kt
+ * Created Time: 2024-01-25
+ * Author: curtishd (1023632660@qq.com)
+ */
+
+package utils
+
+import java.util.*
+
+class Trunk(var prev: Trunk?, var str: String)
+
+/* 打印矩阵（Array） */
+fun <T> printMatrix(matrix: Array<Array<T>>) {
+    println("[")
+    for (row in matrix) {
+        println("  $row,")
+    }
+    println("]")
+}
+
+/* 打印矩阵（List） */
+fun <T> printMatrix(matrix: List<List<T>>) {
+    println("[")
+    for (row in matrix) {
+        println("  $row,")
+    }
+    println("]")
+}
+
+/* 打印链表 */
+fun printLinkedList(h: ListNode?) {
+    var head = h
+    val list = ArrayList<String>()
+    while (head != null) {
+        list.add(head.value.toString())
+        head = head.next
+    }
+    println(list.joinToString(separator = " -> "))
+}
+
+/* 打印二叉树 */
+fun printTree(root: TreeNode?) {
+    printTree(root, null, false)
+}
+
+/**
+ * 打印二叉树
+ * This tree printer is borrowed from TECHIE DELIGHT
+ * https://www.techiedelight.com/c-program-print-binary-tree/
+ */
+fun printTree(root: TreeNode?, prev: Trunk?, isRight: Boolean) {
+    if (root == null) {
+        return
+    }
+
+    var prevStr = "    "
+    val trunk = Trunk(prev, prevStr)
+
+    printTree(root.right, trunk, true)
+
+    if (prev == null) {
+        trunk.str = "———"
+    } else if (isRight) {
+        trunk.str = "/———"
+        prevStr = "   |"
+    } else {
+        trunk.str = "\\———"
+        prev.str = prevStr
+    }
+
+    showTrunks(trunk)
+    println(" ${root.value}")
+
+    if (prev != null) {
+        prev.str = prevStr
+    }
+    trunk.str = "   |"
+
+    printTree(root.left, trunk, false)
+}
+
+fun showTrunks(p: Trunk?) {
+    if (p == null) {
+        return
+    }
+    showTrunks(p.prev)
+    print(p.str)
+}
+
+/* 打印哈希表 */
+fun <K, V> printHashMap(map: Map<K, V>) {
+    for ((key, value) in map) {
+        println(key.toString() + " -> " + value)
+    }
+}
+
+/* 打印堆 */
+fun printHeap(queue: Queue<Int>?) {
+    val list = queue?.let { ArrayList(it) }
+    print("堆的数组表示：")
+    println(list)
+    println("堆的树状表示：")
+    val root = list?.let { TreeNode.listToTree(it) }
+    printTree(root)
+}

codes/kotlin/utils/TreeNode.kt

@@ -0,0 +1,68 @@
+/**
+ * File: TreeNode.kt
+ * Created Time: 2024-01-25
+ * Author: curtishd (1023632660@qq.com)
+ */
+
+package utils
+
+/* 二叉树节点类 */
+class TreeNode(
+    var value: Int // 节点值
+) {
+    var height: Int = 0 // 节点高度
+    var left: TreeNode? = null // 左子节点引用
+    var right: TreeNode? = null // 右子节点引用
+
+    // 序列化编码规则请参考：
+    // https://www.hello-algo.com/chapter_tree/array_representation_of_tree/
+    // 二叉树的数组表示：
+    // [1, 2, 3, 4, None, 6, 7, 8, 9, None, None, 12, None, None, 15]
+    // 二叉树的链表表示：
+    //             /——— 15
+    //         /——— 7
+    //     /——— 3
+    //    |    \——— 6
+    //    |        \——— 12
+    // ——— 1
+    //     \——— 2
+    //        |    /——— 9
+    //         \——— 4
+    //             \——— 8
+
+    /* 将列表反序列化为二叉树：递归 */
+    companion object {
+        private fun listToTreeDFS(arr: MutableList<Int?>, i: Int): TreeNode? {
+            if (i < 0 || i >= arr.size || arr[i] == null) {
+                return null
+            }
+            val root = TreeNode(arr[i]!!)
+            root.left = listToTreeDFS(arr, 2 * i + 1)
+            root.right = listToTreeDFS(arr, 2 * i + 2)
+            return root
+        }
+
+        /* 将列表反序列化为二叉树 */
+        fun listToTree(arr: MutableList<Int?>): TreeNode? {
+            return listToTreeDFS(arr, 0)
+        }
+
+        /* 将二叉树序列化为列表：递归 */
+        private fun treeToListDFS(root: TreeNode?, i: Int, res: MutableList<Int?>) {
+            if (root == null) return
+            while (i >= res.size) {
+                res.add(null)
+            }
+            res[i] = root.value
+            treeToListDFS(root.left, 2 * i + 1, res)
+            treeToListDFS(root.right, 2 * i + 2, res)
+        }
+
+        /* 将二叉树序列化为列表 */
+        fun treeToList(root: TreeNode?): List<Int?> {
+            val res = ArrayList<Int?>()
+            treeToListDFS(root, 0, res)
+            return res
+        }
+    }
+}

codes/kotlin/utils/Vertex.kt

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+/**
+ * File: Vertex.kt
+ * Created Time: 2024-01-25
+ * Author: curtishd (1023632660@qq.com)
+ */
+
+package utils
+
+/* 顶点类 */
+class Vertex(val value: Int) {
+    companion object {
+        /* 输入值列表 vals ，返回顶点列表 vets */
+        fun valsToVets(vals: IntArray): Array<Vertex?> {
+            val vets = arrayOfNulls<Vertex>(vals.size)
+            for (i in vals.indices) {
+                vets[i] = Vertex(vals[i])
+            }
+            return vets
+        }
+
+        /* 输入顶点列表 vets ，返回值列表 vals */
+        fun vetsToVals(vets: List<Vertex?>): List<Int> {
+            val vals = ArrayList<Int>()
+            for (vet in vets) {
+                vals.add(vet!!.value)
+            }
+            return vals
+        }
+    }
+}