1 00:00:00,410 --> 00:00:07,190 ‫So now we're going to write our code for selection sort and we'll pick up where we left off in the last 2 00:00:07,190 --> 00:00:07,880 ‫video. 3 00:00:08,000 --> 00:00:13,160 ‫Except I'll shrink this down into the corner to make room for our code. 4 00:00:13,610 --> 00:00:20,840 ‫So we'll pass this an array of integers, and then we'll also pass this the size of the array. 5 00:00:21,610 --> 00:00:28,420 ‫And we'll start out with this for loop that iterates through the length of the array where AI is equal 6 00:00:28,420 --> 00:00:29,140 ‫to zero. 7 00:00:29,140 --> 00:00:30,940 ‫So I'm going to bring this up. 8 00:00:31,120 --> 00:00:35,050 ‫AI is going to be this index of zero. 9 00:00:35,230 --> 00:00:41,530 ‫And in the last video we started out by setting min index to be equal to zero. 10 00:00:41,800 --> 00:00:46,630 ‫And we're going to do that by setting it to be equal to AI. 11 00:00:46,900 --> 00:00:53,470 ‫So I'm going to shrink this down and min index is going to be an integer and we'll set that to be equal 12 00:00:53,470 --> 00:00:55,840 ‫to I from the for loop. 13 00:00:56,020 --> 00:01:03,010 ‫And now we'll create that second for loop and notice that we're setting J to be equal to AI plus one. 14 00:01:03,640 --> 00:01:05,470 ‫And I'll bring this back up. 15 00:01:05,470 --> 00:01:11,530 ‫We're starting out with AI being equal to zero and J is equal to AI plus one. 16 00:01:11,770 --> 00:01:18,730 ‫So we started out with min index being equal to AI, which in this case is zero. 17 00:01:18,850 --> 00:01:27,190 ‫But we want to change that if we come across a value that's less than the value that stored at min index 18 00:01:27,580 --> 00:01:32,950 ‫and since two is less than four, obviously that is the case here. 19 00:01:33,160 --> 00:01:37,300 ‫So we'll set min index to be equal to J. 20 00:01:37,930 --> 00:01:42,430 ‫So let's shrink this down and bring back our code. 21 00:01:42,910 --> 00:01:52,360 ‫So we'll say if the value at the index of J is less than the value at the index of min index, then 22 00:01:52,360 --> 00:01:55,960 ‫we'll set min index to be equal to J. 23 00:01:56,590 --> 00:02:01,450 ‫And now let's bring this back up and J is equal to one. 24 00:02:01,450 --> 00:02:05,140 ‫So now men index is the index of one. 25 00:02:05,790 --> 00:02:11,280 ‫And now that second for loop is going to move Jay through the end of the array. 26 00:02:11,610 --> 00:02:15,480 ‫So when we move to the next item, six is not less than two. 27 00:02:15,510 --> 00:02:19,920 ‫So we keep looping until we get to here and now. 28 00:02:19,920 --> 00:02:27,000 ‫The item at the index of J is less than the item at the Index of Men Index. 29 00:02:27,300 --> 00:02:33,390 ‫So we set men index to be equal to J, which is the index of four. 30 00:02:33,870 --> 00:02:37,770 ‫And then we continue looping to the end of the array. 31 00:02:38,510 --> 00:02:42,770 ‫So now we know the index that contains the minimum value. 32 00:02:42,770 --> 00:02:45,200 ‫It's that the index of four. 33 00:02:46,060 --> 00:02:48,040 ‫So now we'll swap these. 34 00:02:48,040 --> 00:02:51,670 ‫And when we do this, we know that that first item is sorted. 35 00:02:51,670 --> 00:02:53,980 ‫So I'll colour that in green. 36 00:02:54,520 --> 00:03:00,700 ‫So let's shrink this down and we'll bring in the code that we use to swap those two items. 37 00:03:00,700 --> 00:03:03,220 ‫It's going to be these three lines. 38 00:03:03,490 --> 00:03:09,610 ‫This is very similar to what we did to swap two items in an array and bubble sort. 39 00:03:09,790 --> 00:03:15,340 ‫So I'm not going to walk through these three lines of code because we covered this in bubble sort. 40 00:03:15,730 --> 00:03:19,450 ‫So I'm going to bring this up and walk through this one more time. 41 00:03:19,450 --> 00:03:27,010 ‫When we go through the four loop again, I is moved to that second item in the array and J is going 42 00:03:27,010 --> 00:03:28,660 ‫to be I plus one. 43 00:03:29,460 --> 00:03:36,420 ‫So we're going to set men index to be equal to AI, which in this case is the index of one. 44 00:03:37,190 --> 00:03:43,730 ‫But you can just look at this and see as we move Jay through the array, there are no items that are 45 00:03:43,730 --> 00:03:45,320 ‫less than two. 46 00:03:45,650 --> 00:03:50,690 ‫So we're going to move this all the way through and we're not going to change men index. 47 00:03:51,230 --> 00:03:59,660 ‫So if men index is equal to the same index that I is equal to, that means we don't need to do a swap. 48 00:04:00,140 --> 00:04:04,910 ‫Now, that does mean that the item at the index of one is sorted, so I'll go ahead and colour that 49 00:04:04,910 --> 00:04:06,080 ‫in green. 50 00:04:06,560 --> 00:04:12,440 ‫But our three lines of code that we use for swapping items does not need to be run here. 51 00:04:12,950 --> 00:04:21,110 ‫So we'll create an if statement that says, if I is not equal to men index, only then do we run these 52 00:04:21,110 --> 00:04:22,310 ‫three lines of code. 53 00:04:23,080 --> 00:04:30,430 ‫So now let's add this into the rest of our code, and that is all of the selection sort function. 54 00:04:30,790 --> 00:04:35,740 ‫If we keep running through this, we'll end up with an array that looks like this. 55 00:04:36,160 --> 00:04:39,460 ‫So we'll look at this code in a moment in VTS code. 56 00:04:39,460 --> 00:04:43,870 ‫And when we do, we'll start out with an array that looks like this. 57 00:04:43,990 --> 00:04:47,620 ‫And then we'll run selection sort and sort it. 58 00:04:48,070 --> 00:04:51,160 ‫So now let's flip over and take a look at this. 59 00:04:52,400 --> 00:05:00,860 ‫So there is our selection sort function there and I'm going to scroll up and in our main function this 60 00:05:00,860 --> 00:05:07,910 ‫creates that array that we just saw and this line calculates the size of the array and that we call 61 00:05:07,910 --> 00:05:11,180 ‫selection sort on the array with the size. 62 00:05:11,510 --> 00:05:16,760 ‫And this for loop will loop through that array after it is sorted and print that out. 63 00:05:17,150 --> 00:05:23,660 ‫So now I'll run this and you can see that the array has now been sorted one through six. 64 00:05:24,490 --> 00:05:28,240 ‫And that is our function for selection sort.