Solve "cafe order checker" (again)

Perhaps my fifth iteration of solving this problem.

scratch/facebook/interview-cake/cafe-order-checker.py

@@ -0,0 +1,34 @@
+def valid(take_out, dine_in, served):
+    # edge case
+    if len(take_out) + len(dine_in) != len(served):
+        return False
+    i = 0
+    j = 0
+    k = 0
+    while i < len(take_out) and j < len(dine_in):
+        if take_out[i] == served[k]:
+            i += 1
+        elif dine_in[j] == served[k]:
+            j += 1
+        else:
+            return False
+        k += 1
+    # take out
+    while i < len(take_out):
+        if take_out[i] != served[k]:
+            return False
+        i += 1
+    # dine in
+    while j < len(dine_in):
+        if dine_in[j] != served[k]:
+            return False
+        j += 1
+    return True
+
+take_out = [17, 8, 24]
+dine_in  = [12, 19, 2]
+served   = [17, 8, 12, 19, 24, 2]
+result = valid(take_out, dine_in, served)
+print(result)
+assert result
+print("Success!")