WEBVTT 00:00.640 --> 00:08.020 A common requirement is to have a collection that can be an arbitrary size and can grow and shrink at 00:08.020 --> 00:08.800 runtime. 00:08.800 --> 00:15.880 So the C plus plus standard library provides a various classes to allow you to do this and will be described 00:15.880 --> 00:17.290 in next lecture, of course. 00:17.290 --> 00:25.240 But in this lecture we will create an examples that illustrates some of the principles of how these 00:25.240 --> 00:28.570 standard collections are implemented here. 00:28.570 --> 00:35.890 So in general, you should use the C plus plus standard library classes rather than implementing your 00:35.890 --> 00:37.090 own classes here. 00:37.510 --> 00:45.670 So further, the standard library classes encapsulate code together in a class, and since we have not 00:45.670 --> 00:52.480 covered classes yet, this in this lecture that we're going to create some code. 00:52.510 --> 00:58.960 In this code we're going to use functions that potentially can be called incorrectly. 00:58.960 --> 01:03.410 So you should regard this examples as just that example code here. 01:03.410 --> 01:06.800 So a linked list is a common data structure here. 01:06.800 --> 01:13.190 So these are typically used for queues where the order of items is important. 01:13.190 --> 01:21.260 So for example, a first in, first out queue, where the tasks are performed in the order that they 01:21.260 --> 01:23.180 are inserted in the queue here. 01:23.300 --> 01:31.100 So in this example, each task is represented as a structure that contains the task description and 01:31.100 --> 01:34.070 the pointer to the next task to be performed. 01:34.070 --> 01:42.830 So if a pointer to the next task is nullptr, then this means that the current task is the last task 01:42.830 --> 01:45.230 in the list here. 01:45.230 --> 01:48.500 So struct we're going to create a new struct here. 01:48.530 --> 01:54.290 Of course outside the here struct task here. 01:55.650 --> 02:01.650 And here we're going to task P next and. 02:02.840 --> 02:04.670 We can create another string here. 02:09.750 --> 02:10.410 Here. 02:10.560 --> 02:19.260 So recall this from the last chapter that you can access members of structure using the dot operator 02:19.260 --> 02:29.760 here so we can make it like that task that or let's create a task item and item that description here. 02:29.760 --> 02:33.270 As you can see, we can access their members. 02:33.270 --> 02:36.240 So in this case, the compiler will create a string. 02:37.080 --> 02:40.140 A string object initialized with the string literal. 02:40.800 --> 02:47.430 That means here we're going to initialize it with to something here. 02:48.360 --> 02:54.990 So and it will assign to the description member of the instance called item. 02:54.990 --> 02:58.380 So you can also create a task on the free storage. 02:59.260 --> 03:03.130 Using the new operator like that here, for example. 03:03.130 --> 03:08.350 Task P task and new task here. 03:09.070 --> 03:09.580 Oops. 03:09.870 --> 03:10.750 Uh, task. 03:11.450 --> 03:11.870 Here. 03:11.870 --> 03:23.320 And after using the object, after using the object object, you can delete by this. 03:23.330 --> 03:24.260 Delete. 03:25.210 --> 03:26.740 P task here. 03:26.980 --> 03:27.610 P task. 03:28.690 --> 03:37.720 So here in this case, the members of the object have to be accessed through the pointer and Cplusplus 03:37.720 --> 03:47.440 provides this operator here like that, the minus operator and the right, uh, greater than operator 03:47.440 --> 03:48.010 here. 03:48.530 --> 03:52.690 Uh, this operator gives you this access here. 03:52.810 --> 03:53.800 P task. 03:54.100 --> 03:56.000 P Task here. 03:56.380 --> 03:57.490 Description. 03:57.850 --> 03:59.140 As you can see here. 03:59.140 --> 04:01.120 And do something. 04:02.730 --> 04:03.120 Here. 04:03.330 --> 04:11.730 So here the description member here, here, The description member is assigned to the string. 04:11.730 --> 04:14.970 So not that the science task is a structure. 04:15.640 --> 04:18.160 There is no access restrictions. 04:18.160 --> 04:23.990 So something that is important with classes and described in next lecture here. 04:24.010 --> 04:30.790 So in next in this lecture, we're going to create some project that is going to. 04:35.650 --> 04:38.020 Use this task struct here. 04:39.520 --> 04:41.650 And, um. 04:42.190 --> 04:47.110 And we're going to make the strings and the task next pointers here. 04:47.110 --> 04:49.570 So I'm waiting you in next lecture.