4 files changed, 77 insertions, 0 deletions
diff --git a/challenge-018/orestis-zekai/README b/challenge-018/orestis-zekai/README
new file mode 100644
index 0000000000..7e89e9dd0f
--- /dev/null
+++ b/challenge-018/orestis-zekai/README
@@ -0,0 +1 @@
+Solutions by Orestis Zekai.
diff --git a/challenge-018/orestis-zekai/python/ch-1.py b/challenge-018/orestis-zekai/python/ch-1.py
new file mode 100644
index 0000000000..e997db9e74
--- /dev/null
+++ b/challenge-018/orestis-zekai/python/ch-1.py
@@ -0,0 +1,18 @@
+# Longest common substring
+
+string1 = "ABABC"
+string2 = "BABCA"
+
+max_substring = ""
+max_length = -1
+
+
+for i in range(0, len(string1)+1):
+	for j in range(0, len(string1)+1):
+		if (string1[i:j] in string2) and len(string1[i:j]) > max_length:
+			max_length = len(string1[i:j])
+			max_substring = string1[i:j]
+
+
+print('The longest substring is: ' + max_substring)
+print('The length of the longest substring is: ' + str(max_length))
+\ No newline at end of file
diff --git a/challenge-018/orestis-zekai/python/ch-2.py b/challenge-018/orestis-zekai/python/ch-2.py
new file mode 100644
index 0000000000..ff36bfd529
--- /dev/null
+++ b/challenge-018/orestis-zekai/python/ch-2.py
@@ -0,0 +1,55 @@
+import time
+import math
+
+def is_empty(queue):
+    if not queue:
+        print("Queue is empty")
+    else:
+        print("Queue is not empty")
+
+def insert_with_priority(queue):
+    print('Enter the priority of the element you want to insert')
+    priority = int(input())
+    timestamp = time.time()
+
+    queue.append([priority, timestamp])
+    return queue
+
+def pull_highest_prority_element(queue):
+    queue.remove(max(queue))
+    return queue
+
+available_choices = [1, 2, 3, 4]
+queue = []
+
+while 1:
+    print('\n\n')
+    print('================================')
+    print('Current status of queue')
+    if not queue:
+        print(queue)
+    else:
+        for i in range(0, len(queue)):
+            print(queue[i][0])
+    
+    
+    print('1. Check if queue is empty')
+    print('2. Insert with priority')
+    print('3. Pull highest priority element')
+    print('4. Exit')
+    print('Enter the number of your choice')
+
+    choice = int(input())
+    while (choice not in available_choices):
+        print('Please enter a valid choice')
+        choice = int(input())
+
+    if (choice == 1):
+        is_empty(queue)
+    if (choice == 2):
+        queue = insert_with_priority(queue)
+    if (choice == 3):
+        queue = pull_highest_prority_element(queue)
+    if (choice == 4):
+        break
+
diff --git a/guests.json b/guests.json
new file mode 100644
index 0000000000..f51bf26225
--- /dev/null
+++ b/guests.json
@@ -0,0 +1,3 @@
+{
+    "orestis-zekai" : "Orestis Zekai"
+}