Add Kotlin code for computational complexity (#1090)

* feat(kotlin):new kotlin support files

* fix(kotlin):

    reviewed the formatting, comments and so on.

* fix(kotlin): fix the indentation and format

* feat(kotlin): Add kotlin code for the backtraking chapter.

* fix(kotlin): fix incorrect output of preorder_traversal_iii_template.kt file

* fix(kotlin): simplify kotlin codes

* fix(kotlin): modify n_queens.kt for consistency.

* feat(kotlin): add kotlin code for computational complexity.

* fix(kotlin): remove iteration folder.

* fix(kotlin): remove n_queens.kt file out of folder.

* fix(kotlin): remove some folders.

* style(kotlin): modified two chapters.

codes/kotlin/chapter_computational_complexity/iteration.kt

@@ -0,0 +1,74 @@
+/**
+ * File: iteration.kt
+ * Created Time: 2024-01-25
+ * Author: curtishd (1023632660@qq.com)
+ */
+
+package chapter_computational_complexity.iteration
+
+/* for 循环 */
+fun forLoop(n: Int): Int {
+    var res = 0
+    // 循环求和 1, 2, ..., n-1, n
+    for (i in 1..n) {
+        res += i
+    }
+    return res
+}
+
+/* while 循环 */
+fun whileLoop(n: Int): Int {
+    var res = 0
+    var i = 1 // 初始化条件变量
+    // 循环求和 1, 2, ..., n-1, n
+    while (i <= n) {
+        res += i
+        i++ // 更新条件变量
+    }
+    return res
+}
+
+/* while 循环（两次更新） */
+fun whileLoopII(n: Int): Int {
+    var res = 0
+    var i = 1 // 初始化条件变量
+    // 循环求和 1, 4, 10, ...
+    while (i <= n) {
+        res += i
+        // 更新条件变量
+        i++
+        i *= 2
+    }
+    return res
+}
+
+/* 双层 for 循环 */
+fun nestedForLoop(n: Int): String {
+    val res = StringBuilder()
+    // 循环 i = 1, 2, ..., n-1, n
+    for (i in 1..n) {
+        // 循环 j = 1, 2, ..., n-1, n
+        for (j in 1..n) {
+            res.append(" ($i, $j), ")
+        }
+    }
+    return res.toString()
+}
+
+/* Driver Code */
+fun main() {
+    val n = 5
+    var res: Int
+
+    res = forLoop(n)
+    println("\nfor 循环的求和结果 res = $res")
+
+    res = whileLoop(n)
+    println("\nwhile 循环的求和结果 res = $res")
+
+    res = whileLoopII(n)
+    println("\nwhile 循环 (两次更新) 求和结果 res = $res")
+
+    val resStr = nestedForLoop(n)
+    println("\n双层 for 循环的遍历结果 $resStr")
+}