1 00:00:00,450 --> 00:00:04,650 ‫So now we're going to write our function for delete first. 2 00:00:05,220 --> 00:00:10,860 ‫So I'm going to bring up a linked list and with delete first we're going to move head over and we're 3 00:00:10,860 --> 00:00:13,410 ‫going to delete that first node. 4 00:00:13,740 --> 00:00:20,550 ‫And just like with delete last, we have an edge case for when we have one node in the linked list. 5 00:00:20,550 --> 00:00:25,590 ‫And then we also have an edge case for when we have an empty linked list. 6 00:00:26,190 --> 00:00:28,570 ‫So we'll start our function out like this. 7 00:00:28,590 --> 00:00:35,070 ‫We'll call it delete first and the first situation will code for is when we have an empty linked list. 8 00:00:35,680 --> 00:00:42,400 ‫So we'll say if the length is equal to zero will run return, which will break us out of the function. 9 00:00:42,610 --> 00:00:49,690 ‫And instead of saying if length is equal to zero, you could say if the head is equal to null pointer. 10 00:00:50,490 --> 00:00:54,750 ‫So now this code for when we have one item in the linked list. 11 00:00:55,050 --> 00:00:57,960 ‫First, we're going to set temp to be equal to head. 12 00:00:57,960 --> 00:01:04,140 ‫We'll do that with this line of code and then we'll say if the length is equal to one, we'll set head 13 00:01:04,140 --> 00:01:06,630 ‫and tail to be equal to null pointer. 14 00:01:06,960 --> 00:01:08,970 ‫And that does this. 15 00:01:09,390 --> 00:01:12,360 ‫So let's add this in with the rest of our code. 16 00:01:12,630 --> 00:01:15,480 ‫So this is for when we have an empty length list. 17 00:01:15,480 --> 00:01:21,480 ‫This is if we have one item and then if we have two or more items, we'll say else. 18 00:01:21,480 --> 00:01:24,450 ‫And now let's build out this else statement. 19 00:01:24,870 --> 00:01:28,320 ‫So we'll say head equals head next. 20 00:01:28,320 --> 00:01:36,990 ‫That is head next, and that moves that over and then we'll say delete temp and that will remove that 21 00:01:36,990 --> 00:01:41,460 ‫node from memory and then we'll decrement the length by one. 22 00:01:41,970 --> 00:01:48,120 ‫So now let's put this in with the rest of our code, and that is the entire delete first function. 23 00:01:48,420 --> 00:01:51,300 ‫So we'll look at this code in a moment and VS code. 24 00:01:51,300 --> 00:01:58,290 ‫And when we do, we'll build this linked list we want to test to make sure this code works when we have 25 00:01:58,320 --> 00:02:04,320 ‫two or more items and then if it has one item and then we'll run it again to make sure it works on an 26 00:02:04,320 --> 00:02:05,940 ‫empty linked list. 27 00:02:06,180 --> 00:02:09,630 ‫So now let's flip over and take a look at this. 28 00:02:10,260 --> 00:02:18,300 ‫So there is our delete first member function added to our linked list class and I'll scroll up and in 29 00:02:18,300 --> 00:02:24,630 ‫our main function with these two lines, we create that linked list with values of two and one, and 30 00:02:24,630 --> 00:02:26,190 ‫I'll scroll up again. 31 00:02:26,520 --> 00:02:29,430 ‫So this will print out our link list before we run. 32 00:02:29,430 --> 00:02:33,300 ‫Delete first and this will show our link list after we run. 33 00:02:33,300 --> 00:02:39,600 ‫Delete first the first time and this is going to be the second time and the third time with the third 34 00:02:39,600 --> 00:02:42,240 ‫time being on an empty linked list. 35 00:02:42,450 --> 00:02:49,350 ‫So I'll run this and you can see over here, this is our linked list before we removed any items and 36 00:02:49,350 --> 00:02:53,370 ‫then after we removed one item and then we did it again. 37 00:02:53,370 --> 00:02:55,410 ‫And now the length list is empty. 38 00:02:55,650 --> 00:02:59,730 ‫And then the third time we ran delete first on an empty linked list. 39 00:02:59,730 --> 00:03:04,680 ‫And that means this is working on all three of the situations that we're testing for. 40 00:03:05,070 --> 00:03:10,350 ‫And that means we have a working function for delete first.