1 00:00:00,390 --> 00:00:03,810 ‫So now we're going to build our hash table constructor. 2 00:00:04,230 --> 00:00:11,070 ‫So I'm going to bring up an address space here, except I'm going to make a change to the address space. 3 00:00:11,070 --> 00:00:17,460 ‫Instead of having eight items, I'm going to remove the item on the bottom and we're only going to have 4 00:00:17,460 --> 00:00:18,300 ‫seven. 5 00:00:18,720 --> 00:00:24,240 ‫I want to do this to emphasize that your address space, whatever size that you make it, you should 6 00:00:24,240 --> 00:00:26,280 ‫make it a prime number. 7 00:00:26,520 --> 00:00:33,630 ‫And the reason for that is if you have a prime number of addresses, your key value pairs will be distributed 8 00:00:33,630 --> 00:00:34,860 ‫more randomly. 9 00:00:35,010 --> 00:00:37,740 ‫In other words, you'll have fewer collisions. 10 00:00:38,010 --> 00:00:45,300 ‫So we'll start our hash table class off like this, and we're going to have a couple of member variables. 11 00:00:45,510 --> 00:00:53,100 ‫And I like to explicitly make these private, even though they will be private by default and our first 12 00:00:53,100 --> 00:00:59,370 ‫variable will call size, we'll set that to be equal to seven and that's going to be the size of the 13 00:00:59,370 --> 00:01:05,400 ‫array that we're using for our address space because we are assigning the value here. 14 00:01:05,490 --> 00:01:07,940 ‫We're going to make it a constant. 15 00:01:07,950 --> 00:01:14,280 ‫And because it is a constant, a common naming convention is to make the variable name. 16 00:01:14,280 --> 00:01:21,050 ‫All caps and static means that we're only going to store one of these numbers sevens in memory. 17 00:01:21,060 --> 00:01:27,630 ‫So if we create two hash tables, let's say we call them my hash table one and my hash table two. 18 00:01:27,960 --> 00:01:35,550 ‫Both of those instances of hash table will use this one, number seven, and now we'll create that address 19 00:01:35,550 --> 00:01:36,450 ‫space. 20 00:01:36,480 --> 00:01:38,520 ‫I'm going to call it data map. 21 00:01:38,520 --> 00:01:41,850 ‫And the size is going to be this size here. 22 00:01:41,940 --> 00:01:47,280 ‫And the data map is going to hold pointers to nodes like this. 23 00:01:47,670 --> 00:01:53,970 ‫So I called this video constructor, but technically, this hash table class does not have a constructor. 24 00:01:54,180 --> 00:02:00,450 ‫All we're doing is using these two lines to create this data map, address space. 25 00:02:00,810 --> 00:02:06,420 ‫Remember, technically, a constructor would be a separate function with the name of the class. 26 00:02:06,750 --> 00:02:13,800 ‫But we don't need that here because this is all we're going to do when we create a new hash table. 27 00:02:14,130 --> 00:02:18,180 ‫So the other thing we need to be able to create is nodes. 28 00:02:18,450 --> 00:02:24,090 ‫So these nodes are going to be a little bit different than what we saw in the linked list section. 29 00:02:24,270 --> 00:02:27,930 ‫These nodes are going to have key and value. 30 00:02:27,930 --> 00:02:34,560 ‫And next in the linked list section, the nodes just had value index, but they didn't have key. 31 00:02:34,770 --> 00:02:41,670 ‫So in our node class, there are going to be three member variables, key value and next. 32 00:02:41,940 --> 00:02:46,920 ‫And in the constructor we will pass it a key and a value. 33 00:02:47,100 --> 00:02:51,720 ‫This key and value are going to be these variables here. 34 00:02:51,930 --> 00:02:55,860 ‫And we'll set this key and this value equal to those. 35 00:02:55,860 --> 00:03:01,890 ‫And this key and this value will be the member variables for the class. 36 00:03:02,190 --> 00:03:06,810 ‫And then the last thing is we'll set next to be equal to null pointer. 37 00:03:07,200 --> 00:03:12,630 ‫So we've written the code in the hash table class to create the address space and then with the node 38 00:03:12,630 --> 00:03:16,110 ‫class, the ability to create nodes. 39 00:03:16,380 --> 00:03:20,070 ‫So now let's flip over to VS code and take a look at this. 40 00:03:20,850 --> 00:03:28,410 ‫So there is our node class there and I'm going to scroll up and this is the code that we just wrote 41 00:03:28,410 --> 00:03:30,030 ‫for the hash table class. 42 00:03:30,150 --> 00:03:35,700 ‫And just like I have done previously, I've created a function to be able to print out whatever the 43 00:03:35,700 --> 00:03:37,650 ‫data structure is that we're building. 44 00:03:37,680 --> 00:03:40,080 ‫I'm going to call this one print table. 45 00:03:40,530 --> 00:03:46,920 ‫I won't walk through the detail of this code, but you can access this code and the resources tab for 46 00:03:46,920 --> 00:03:50,100 ‫this video and then I'll scroll up again. 47 00:03:50,580 --> 00:03:55,500 ‫So with this line here, we create a new hash table, and then with this line here, we'll print that 48 00:03:55,500 --> 00:04:01,500 ‫table out and I'll run this and you can see our addresses here zero through six. 49 00:04:01,500 --> 00:04:05,730 ‫We haven't added any key value pairs yet, so these are all empty. 50 00:04:06,450 --> 00:04:11,580 ‫But it does look like we have a working hash table constructor.