Implement 'q_ascend'

Implement 'q_ascend'
function using the
Linux Kernel API.

Change-Id: I2f2d4df6810eb3339c3de547904388d7fc313d1a

Author: PoChuan994

queue.c

@@ -245,7 +245,33 @@ void q_sort(struct list_head *head, bool descend) {}
 int q_ascend(struct list_head *head)
 {
     // https://leetcode.com/problems/remove-nodes-from-linked-list/
-    return 0;
+    element_t *curr = NULL, *prev = NULL;
+    const element_t *target;
+    struct list_head *pos = NULL;
+
+    if (!head || list_empty(head) || list_is_singular(head))
+        return 0;
+
+    list_for_each_entry (curr, head, list) {
+        /* Release the element in the next round */
+        if (prev) {
+            q_release_element(prev);
+            prev = NULL;
+        }
+
+        /* check right side and find if there is greater value */
+        if (curr->list.next)
+            pos = curr->list.next;
+        for (; pos != head; pos = pos->next) {
+            target = list_entry(pos, element_t, list);
+            if (strcmp(curr->value, target->value) > 0) {
+                list_del(&curr->list);
+                prev = curr;
+                break;
+            }
+        }
+    }
+    return q_size(head);
 }
 
 /* Remove every node which has a node with a strictly greater value anywhere to
@@ -261,5 +287,22 @@ int q_descend(struct list_head *head)
 int q_merge(struct list_head *head, bool descend)
 {
     // https://leetcode.com/problems/merge-k-sorted-lists/
-    return 0;
+    if (!head || list_empty(head))
+        return 0;
+    if (list_is_singular(head))
+        return q_size(list_first_entry(head, queue_contex_t, chain)->q);
+
+    queue_contex_t *first, *target = NULL;
+    first = list_first_entry(head, queue_contex_t, chain);
+
+    /* move each target's queue to first context's queue */
+    list_for_each_entry (target, head->next, chain) {
+        if (target->id == first->id)
+            break;
+        list_splice_tail_init(target->q, first->q);
+    }
+    q_sort(first->q, descend);
+    head = first->q;
+
+    return q_size(head);
 }