Bug fixes and improvements (#1472)

* preorder, inorder, postorder -> pre-order, in-order, post-order

* Bug fixes

* Bug fixes

* Update what_is_dsa.md

* Sync zh and zh-hant versions

* Sync zh and zh-hant versions.

* Update performance_evaluation.md and time_complexity.md

* Add @khoaxuantu to the landing page.

* Sync zh and zh-hant versions

* Add @ khoaxuantu to the landing page of zh-hant and en versions.

* Sync zh and zh-hant versions.

* Small improvements

* @issue :  #1450 (#1453)

Fix writing "obsecure" to "obscure"

Co-authored-by: Gaya <kheliligaya@gmail.com>

* Update the definition of "adaptive sorting".

* Update n_queens_problem.md

* Sync zh, zh-hant, and en versions.

---------

Co-authored-by: Gaya-Khelili <50716339+Gaya-Khelili@users.noreply.github.com>
Co-authored-by: Gaya <kheliligaya@gmail.com>

zh-hant/codes/go/chapter_stack_and_queue/array_deque.go

@@ -72,6 +72,9 @@ func (q *arrayDeque) pushLast(num int) {
 /* 佇列首出列 */
 func (q *arrayDeque) popFirst() any {
 	num := q.peekFirst()
+	if num == nil {
+		return nil
+	}
 	// 佇列首指標向後移動一位
 	q.front = q.index(q.front + 1)
 	q.queSize--
@@ -81,6 +84,9 @@ func (q *arrayDeque) popFirst() any {
 /* 佇列尾出列 */
 func (q *arrayDeque) popLast() any {
 	num := q.peekLast()
+	if num == nil {
+		return nil
+	}
 	q.queSize--
 	return num
 }