WEBVTT 00:00.650 --> 00:04.010 In order to solve the problems we're going to come across. 00:04.010 --> 00:11.330 We need to come up with a language or writing algorithm as a way to write down or algorithms so it's 00:11.330 --> 00:14.890 logical and easy to follow. 00:14.890 --> 00:21.370 Last time I said we should first write her algorithms in a way that's easy for us humans to understand 00:22.210 --> 00:29.710 and we could write them in English or whatever language is easiest for you and we will do this in some 00:29.710 --> 00:30.680 parts. 00:30.730 --> 00:37.630 But I want to start transitioning into a real computer language and get used to how it will really work. 00:38.550 --> 00:45.630 We're going to go through some problems and examples and come up with the constructs we'll need for 00:45.630 --> 00:49.380 our algorithms language. 00:49.390 --> 00:52.200 So here's our first problem. 00:52.240 --> 01:01.180 It says writing algorithm that gets Celsius value from the user and outputs that Celsius value in Fahrenheit. 01:01.600 --> 01:08.080 So like I said before the first thing we need to do is understand the problem. 01:08.150 --> 01:12.900 So the first thing it says is get the Celsius value. 01:12.950 --> 01:19.190 So we need some kind of way to get things from the user. 01:19.190 --> 01:27.810 So our very first part of the algorithm will be it's going to say we're just going to start in English 01:27.810 --> 01:35.970 here and get the Celsius. 01:36.130 --> 01:36.810 Now you 01:40.500 --> 01:44.940 user. 01:45.060 --> 01:47.360 So that's the very first thing we should do. 01:48.290 --> 01:56.540 Now a bit more subtly We need to somehow save that Celsius value so we can actually use it. 01:57.050 --> 02:01.270 So to say store 02:04.530 --> 02:05.820 Celsius 02:08.100 --> 02:12.260 now you in two 02:16.740 --> 02:23.800 and sign it two values see. 02:23.820 --> 02:33.570 So we need some kind of way of both naming our values and giving them some and giving them value. 02:33.880 --> 02:41.650 So that's what the sign is it gives it the value and sees just the name of our value that we're going 02:41.650 --> 02:43.160 to use. 02:43.210 --> 02:47.760 This is just like variables in math. 02:48.180 --> 02:50.760 Let's say so. 02:51.160 --> 02:59.420 Next we need to calculate the Fahrenheit value as we know we know see now we have it. 02:59.810 --> 03:09.820 So we need to actually do the calculation so we know that see times 9 03:13.610 --> 03:26.630 over 5 plus 32 will give us the Fahrenheit that. 03:26.700 --> 03:36.110 So now we know that we need some kind of semblance of doing arithmetic operations like multiply divide 03:37.690 --> 03:41.360 addition and subtraction. 03:41.430 --> 03:47.980 So the next thing we need to do is sign store 03:52.580 --> 03:54.590 value from three 03:57.860 --> 04:04.330 step three in which to say the value 04:10.460 --> 04:10.820 right. 04:10.820 --> 04:15.970 So we're kind of doing what we did in step 2 but now we're going to make a new value called afferent 04:15.980 --> 04:18.830 a sign at 3s. 04:19.040 --> 04:24.650 Step three. 04:24.680 --> 04:27.320 So the last thing we'll do is output 04:31.350 --> 04:32.510 Okay. 04:32.630 --> 04:37.460 Now we have to ask yourself does this solve the problem. 04:37.650 --> 04:45.150 So let's go through one more time let's get the Celsius value from user in store that sells its value 04:45.150 --> 04:47.180 and assign it to some value. 04:47.180 --> 04:58.540 See then actually do the calculation and assign and store the value from our previous step into the 04:58.540 --> 04:59.420 value. 05:00.370 --> 05:08.060 And then finally output so does this solve the problem. 05:08.070 --> 05:08.870 I think so. 05:08.880 --> 05:17.150 I think we're I think this works and it's good enough for us to have as an algorithm so we can translate 05:17.150 --> 05:19.850 it to a computer. 05:19.880 --> 05:21.910 So what are the takeaways. 05:23.580 --> 05:31.990 At are needed or that we can add to our language well we need some way 05:35.630 --> 05:38.670 of getting input. 05:38.770 --> 05:40.120 Right now we'll just say 05:43.280 --> 05:52.200 something like get input as our construct number one. 05:52.210 --> 05:55.000 Number two we need some way of 05:58.850 --> 06:05.660 naming and storing values. 06:09.090 --> 06:11.040 That's what we didn't stop to remember. 06:11.040 --> 06:16.920 And step four and we need 06:20.100 --> 06:20.800 arithmetic 06:23.620 --> 06:24.580 expressions 06:27.610 --> 06:29.980 like we did in part 3. 06:31.320 --> 06:33.280 These are just the math symbols 06:37.050 --> 06:43.660 and they'll be a few more that we'll need but for now this is this works. 06:43.690 --> 06:45.130 And lastly we need 06:47.900 --> 06:51.230 some way of outputting 06:54.980 --> 06:56.010 results. 06:57.320 --> 07:05.220 So if you remember in the mental model lecture this works exactly. 07:06.100 --> 07:08.670 The way that I outlined. 07:08.710 --> 07:12.050 So we have the input that's that's one here. 07:12.130 --> 07:28.030 One this this line and then we actually go into the algorithm which is step two step three and step 07:28.030 --> 07:35.820 four and then we have the output which is the last part of our mental model. 07:36.180 --> 07:39.050 So see how this mental model really applies here. 07:43.530 --> 07:46.160 So let's go to a new problem. 07:49.950 --> 07:53.590 So say rates an algorithm 07:56.730 --> 08:06.660 that takes two numbers from the user and outputs the bigger number 08:10.250 --> 08:18.710 so using what we have from one problem one is to 08:24.320 --> 08:26.050 you know how to start. 08:26.070 --> 08:43.230 So get a number from the user an sign that each to call it and one we have to choose that. 08:44.060 --> 08:51.130 And then again get a number from the user and sign it 08:53.790 --> 08:55.760 into. 08:55.770 --> 09:01.280 So those are the first two things we need to numbers so we have going into those numbers. 09:03.230 --> 09:08.410 Now we need some way of comparing two values. 09:08.450 --> 09:22.390 So if you make a comparison between one and 2 let's say we checked this comparison. 09:22.390 --> 09:27.750 This gives you well it's either true or false. 09:27.750 --> 09:29.790 This evaluates either true or false. 09:29.790 --> 09:33.670 Either one is greater than two or it's not. 09:33.690 --> 09:41.100 So this is our very first condition and conditions either evaluate teacher or false. 09:41.100 --> 09:49.680 Like I said just like in math we can we can do this kind of comparison with in this case the greater 09:49.680 --> 09:54.590 than sign is the greater than sign. 09:54.840 --> 10:03.300 Not only that though we need some kind of control flow in this case. 10:03.300 --> 10:16.610 It can either be an one that's bigger than two or it can be in two that's greater than in one in thus 10:16.610 --> 10:19.650 we have two different conditions. 10:19.910 --> 10:26.800 So in this case let's say we have and one is greater than two. 10:26.800 --> 10:30.100 So we would output 10:33.170 --> 10:42.030 and want but there's a different condition that says and 2 is greater than 1 and then we would output 10:44.600 --> 10:53.650 in two so see how we have two different paths of execution. 10:53.650 --> 10:57.700 This is called so or two different cases. 10:57.700 --> 10:58.990 This is case one 11:04.630 --> 11:07.920 and this is case two. 11:10.990 --> 11:13.760 Two. 11:13.960 --> 11:25.840 So we need to somehow have a way of deciding which one it is and how we're going to simplify this is 11:26.340 --> 11:29.560 I'm going to say if 11:32.410 --> 11:42.900 anyone is greater than two then what output and one and this will be all part of the same expression. 11:42.920 --> 11:45.900 So to say otherwise 11:49.080 --> 12:00.110 output into should have then output in one. 12:00.110 --> 12:09.470 So this is one of the tougher things to explain actually actually but just know that there's there's 12:09.470 --> 12:10.910 different paths. 12:11.060 --> 12:17.030 If you have a condition like this this is our condition. 12:19.120 --> 12:23.080 In one it's created into 12:25.650 --> 12:30.440 so that's really it that's our outrage. 12:30.580 --> 12:31.510 So let's see. 12:31.510 --> 12:33.110 Does this work. 12:33.220 --> 12:41.770 So get the number from the user and one and then get another number from the user say and two and then 12:41.770 --> 12:47.650 we'll spell check if and one is greater than and two then output and one. 12:48.010 --> 12:58.480 Otherwise I'll put into this I think solves the problem that is that was asked of us. 12:58.650 --> 13:03.480 So what are the takeaways from here. 13:10.390 --> 13:18.980 So rhenium some conditional 13:21.330 --> 13:29.510 statements that's evaluate to TRUE or FALSE. 13:33.510 --> 13:36.330 That's the condition. 13:36.460 --> 13:42.580 Take away five say take away six. 13:43.280 --> 13:45.590 We need some kind of 13:48.180 --> 13:49.270 control flow 13:52.190 --> 13:55.480 for the different cases. 13:56.390 --> 13:58.040 That we can have 14:00.520 --> 14:08.450 based on condition. 14:08.590 --> 14:14.020 Don't worry too much if you're not completely following this yet we'll be doing a lot of examples. 14:14.030 --> 14:18.740 So you'll you'll get it. 14:18.750 --> 14:22.550 So let's move on to the last problem. 14:22.560 --> 14:27.850 Do this lecture this problem re 14:32.250 --> 14:33.570 consumer space 14:37.510 --> 14:37.890 here. 14:37.900 --> 14:42.010 So given the word 14:47.260 --> 14:48.220 Mississippi 14:58.050 --> 14:59.010 count how many 15:03.100 --> 15:04.520 S's here. 15:07.770 --> 15:08.300 In the word 15:13.170 --> 15:16.540 create algorithm. 15:18.140 --> 15:19.320 So you do. 15:23.900 --> 15:32.380 So of course we know just by looking how many S's there should be it should be only for but that's using 15:32.380 --> 15:40.990 our eyes and computers don't have eyes so we need to somehow have an algorithm that will actually go 15:40.990 --> 15:45.960 through and count how many S's that appear. 15:46.390 --> 15:50.890 So how would we start this well. 15:52.820 --> 15:56.280 We would need some kind of counter to actually count. 15:56.280 --> 16:08.260 So let's say counter jurors see will assign value zero for now. 16:08.350 --> 16:08.750 Right. 16:08.810 --> 16:10.550 Because we started zero. 16:10.790 --> 16:15.340 You don't know how many is here yet. 16:15.420 --> 16:18.680 So counters see assigned to value zero. 16:18.900 --> 16:24.440 So the second step we will start at the beginning 16:30.520 --> 16:39.650 and sign current search letter. 16:39.730 --> 16:48.620 This will be of value to be the first letter in the word. 16:48.760 --> 16:49.100 Right. 16:49.180 --> 16:59.710 So the first letter in the word is M. in we will name the current letter to me. 16:59.730 --> 17:03.480 Let's just call it El. 17:03.510 --> 17:06.140 The first letter is L.. 17:09.450 --> 17:14.620 So then we'll have to go through the entire word 17:24.380 --> 17:25.490 in check 17:29.410 --> 17:42.410 if current word or current letter is an --. 17:42.520 --> 17:43.600 Right. 17:43.700 --> 17:49.830 So this is the condition just like we had in problem too. 17:50.250 --> 17:52.030 So we have a condition here. 17:52.350 --> 18:02.800 So if you have a condition then you may have multiple cases so let's just say if current letter 18:06.660 --> 18:07.110 now 18:10.580 --> 18:11.930 is as 18:17.590 --> 18:24.150 then what you should increase the count right. 18:24.210 --> 18:32.090 Crease C by 1 so you add one in as we see in X 18:36.570 --> 18:42.940 and then I guess go to the next letter 18:47.030 --> 18:54.110 and sign it to L. right. 18:54.300 --> 18:57.460 Else you can get the next letter in the word. 18:57.770 --> 18:58.110 So 19:00.810 --> 19:07.240 m so started em good eye or count would not have increased yet. 19:07.560 --> 19:15.790 CS The first asks the count goes to one second as the count goes to season I doesn't count anything 19:15.790 --> 19:16.430 at all. 19:17.300 --> 19:23.850 And then sees an excess of 3 4 and then nothing else right. 19:23.870 --> 19:42.650 Because none of these letters are in S So the takeaway from this is not some kind of way to weigh you 19:44.730 --> 19:54.210 do you know steps multiple times in programming. 19:54.210 --> 19:55.250 Call this a 20:00.820 --> 20:08.690 so we loop through each letter of the word and runs some some steps. 20:08.690 --> 20:16.850 So in this case really the step that we're going to be doing is doing this case in this case doesn't 20:16.850 --> 20:18.080 have an otherwise 20:25.240 --> 20:35.880 there's no otherwise do something we don't really care if it's not an X we just want to keep going. 20:35.880 --> 20:44.410 Great. 20:44.520 --> 20:46.790 That's really all we need for now. 20:49.280 --> 20:57.920 In Don't worry about if you're not really understanding this we'll we'll be going over this a lot and 20:57.920 --> 20:59.650 doing a lot of practice. 20:59.670 --> 21:07.640 So in the next lecture will dive a bit even deeper and really start to formalize this language. 21:07.680 --> 21:09.440 Given the takeaways that you've learned.