WEBVTT 00:00.330 --> 00:07.470 So let's use our takeaways we learned from The Last Lecture we really formalize our language into what 00:07.470 --> 00:10.480 is called pseudo. 00:10.730 --> 00:15.990 So it's starch. 00:16.200 --> 00:20.230 So we'll supreme one get two numbers from the user. 00:20.250 --> 00:23.790 One is the length of the base of a triangle. 00:23.910 --> 00:35.280 The other is the height of the trying to calculate the area of the triangle and output so let's say 00:36.760 --> 00:40.660 we use B for base. 00:40.750 --> 00:52.890 This is our let's call the variable and want to use the call sign as assignment and so use a signed 00:55.040 --> 00:57.380 the user inputs 00:59.960 --> 01:07.670 or the base trying. 01:07.740 --> 01:19.680 So this gets the input from the user and assigns it to our new variable The is just a shorthand that 01:19.680 --> 01:26.290 we understand as assignment in storing the value. 01:26.350 --> 01:31.620 So we do the same for each We'll call the heights. 01:31.690 --> 01:43.890 Each user inputs for the base or heights or the trying 01:50.490 --> 01:51.590 next. 01:52.430 --> 02:00.140 You say A is equal to A is the area. 02:00.140 --> 02:08.230 So do simple calculation times each then all over 2. 02:08.360 --> 02:15.100 So that will calculate the area. 02:15.350 --> 02:21.740 China and then simply all we have to do now is it. 02:21.830 --> 02:28.780 So output the. 02:28.890 --> 02:37.020 And that's our algorithm for calculating the area of trying pretty simple. 02:37.260 --> 02:46.240 And now notice we're really trying to formalize and make a shorthand of our algorithm. 02:46.290 --> 02:50.790 So this is what's called pseudo code. 02:50.860 --> 02:57.760 It's a combination of English because we don't know how to get input from a user yet. 02:58.000 --> 03:05.770 So we just use English and actual code that you might see in a C++. 03:05.780 --> 03:11.890 So here is the value that we get for the base of the triangle. 03:11.900 --> 03:18.240 Each is the height and a is the area. 03:18.470 --> 03:24.740 And again we'll use equals as the sign that. 03:24.860 --> 03:32.390 So this whatever this value evaluates to gets assigned to a 03:36.520 --> 03:39.700 A will have that value after this is over. 03:43.860 --> 03:46.190 And we'll be doing a lot more examples. 03:48.680 --> 03:53.530 Let's move on to problem to. 03:53.610 --> 04:04.730 So given the given three side lengths the triangle A B and C output whether the triangle is equal lateral 04:04.770 --> 04:14.000 which means all sides of the same Isosceles which means two sides of the same or scaling meaning none 04:14.000 --> 04:16.460 of the so 04:20.840 --> 04:25.720 here we know we need some kind of condition right. 04:25.880 --> 04:32.200 So we need to say are all of the sides equal. 04:32.400 --> 04:35.690 If so then it's an equilateral triangle. 04:36.750 --> 04:38.870 So how would you do that. 04:38.910 --> 04:46.800 Well let's just say if a 04:49.980 --> 04:55.930 is in parentheses here is equal to. 04:56.170 --> 04:58.110 We'll just use English here. 04:58.990 --> 05:01.630 He could to the 05:05.990 --> 05:15.890 and the is equal to see 05:18.300 --> 05:30.460 then we know that a is also equal to see because it be equal C and A equals B then A also has to equal 05:30.460 --> 05:39.070 C then we'll say one a is out put 05:43.180 --> 05:46.570 that it's lateral 05:51.790 --> 05:53.900 or All right. 05:57.390 --> 05:57.890 OK. 05:57.990 --> 06:15.140 So this whole thing is all line valuate to True or false and it evaluates true if B is equal to A and 06:15.320 --> 06:21.730 B is also a C and then if it is true then it will do this line. 06:21.840 --> 06:26.010 But that it's an equal try 06:29.340 --> 06:29.850 so. 06:29.920 --> 06:31.000 Otherwise 06:35.510 --> 06:35.810 if 06:41.360 --> 06:46.610 a is equal to B or 06:49.330 --> 06:59.070 A is equal to C or B is equal to C 07:05.380 --> 07:05.890 then 07:11.740 --> 07:21.850 it's at it's an sauce so it's right. 07:23.230 --> 07:23.890 So no. 07:23.940 --> 07:27.850 So notice here is that space. 07:27.870 --> 07:42.670 What does this saying it says if a is equal to B meaning these two sides are the same or azy could see 07:42.670 --> 07:50.070 meaning those two sides of the same or Veazey could see which means those two sides of the same. 07:50.200 --> 07:57.400 Any one of these conditions if they're true means that it's an isosceles triangle and there is here 07:57.400 --> 08:03.600 that they can't all be true because otherwise it would have done this. 08:03.970 --> 08:05.530 This first line right here 08:08.520 --> 08:18.430 so we know that they can't all be the same because it would have said with equal lateral trying. 08:18.570 --> 08:25.280 So we know only two or less are equal here. 08:26.280 --> 08:31.920 And there was also that we can you can actually change conditions together. 08:32.010 --> 08:33.320 So this is a condition. 08:33.330 --> 08:35.030 This artery here. 08:38.510 --> 08:40.360 Right there also. 08:40.390 --> 08:49.780 This is condition and this is also a condition in chaining. 08:49.870 --> 08:58.550 So either one of the either one of these is true then we'll do this again don't worry too much will 08:58.550 --> 09:05.100 go much more formally into into conditions later. 09:05.130 --> 09:10.320 But I just want to give you a little bit of exposure to it now so you'll have a better understanding 09:10.400 --> 09:11.020 later. 09:12.190 --> 09:13.780 So otherwise 09:21.410 --> 09:32.370 an output such output at it's scaley 09:36.860 --> 09:37.250 shreiking 09:42.180 --> 09:52.610 because now we know that none of them could be the same because otherwise if one or more were the same 09:52.700 --> 09:59.910 it would have been it would have done this condition great. 09:59.940 --> 10:11.030 So stips this if it's not all equal skips this if two are equal otherwise they don't just say it's descaling 10:11.150 --> 10:14.380 because none are equal. 10:14.390 --> 10:23.490 Hope you're sort of understanding now how how we're going to go about writing these algorithms and solving 10:23.490 --> 10:24.530 these problems. 10:31.310 --> 10:35.660 So let's move on to three 10:41.410 --> 10:46.560 Supremes three says output all even numbers from 1 to 100. 10:47.840 --> 11:01.200 So we need to go through all of the numbers somehow and see if they are even in if they are we have 11:01.200 --> 11:13.540 the output that number so for this we'll need what we talked about last time which is a so we're some 11:13.550 --> 11:22.550 say loop from 1 to 100. 11:22.780 --> 11:29.350 And notice here that this is also a condition but this is a bit of a different condition than the one 11:29.350 --> 11:32.070 we had here. 11:33.570 --> 11:36.840 This is actually the stopping condition 11:40.490 --> 11:48.820 for our if he didn't have this condition or you wrote it incorrectly it could loop forever. 11:48.830 --> 11:56.120 Remember what I said about computers and them being really dumb computer only does what you tell it 11:56.120 --> 11:56.460 to do. 11:56.460 --> 12:06.270 So if you told them to do or told it to loop infinitely it will loop infinity which is not what you 12:06.270 --> 12:07.230 want. 12:07.380 --> 12:10.840 So reading this condition is very important. 12:12.170 --> 12:18.600 And the conditions for loops are always the stopping condition to do it. 12:18.620 --> 12:23.980 Until this is false. 12:24.100 --> 12:28.770 So now what would we need here. 12:28.780 --> 12:34.470 So we need the current number that were at. 12:34.480 --> 12:37.080 So this is seen. 12:37.420 --> 12:40.080 Will just say is the current number. 12:40.120 --> 12:41.600 Not sure how we get that yet. 12:41.680 --> 12:45.930 But it's whatever the next number is. 12:45.950 --> 12:49.180 So it will start at 1 and they go that 2 in and so on. 12:50.270 --> 12:54.280 So we have the current number and then we'll say 12:57.640 --> 13:02.850 if C-n is exactly 13:05.300 --> 13:18.280 divisible by 2 meaning if it's a whole the whole number it's an actual number so 10 divided by two is 13:18.330 --> 13:28.500 five but nine divided by two is 4.5 great which is not a whole number. 13:30.340 --> 13:40.280 So you want it to exactly divisible by two just to divide something by two you know. 13:42.450 --> 13:43.520 3a then 13:46.600 --> 13:50.340 we'll be pre-suppose output. 13:51.470 --> 13:57.080 The current number of your kids we know the current number is divisible by two. 13:57.080 --> 14:06.520 In this case we don't need it Kate another case because we just want to continue on with the loop. 14:06.520 --> 14:19.660 It's not divisible by two so hopefully you're understanding how this is how this is working. 14:20.960 --> 14:22.910 So you have your stopping condition for you. 14:22.910 --> 14:27.090 Luke So we're going to loop until we get to 100. 14:27.960 --> 14:37.670 We somehow get the current number that we're at and then you say if that current number that we're at 14:37.670 --> 14:45.190 is divisible by 2 then we just output that number. 14:45.780 --> 14:47.230 That's all there is to that. 14:51.240 --> 14:54.320 Sue let's move on to problem for 14:56.940 --> 15:03.410 so get the number from the user and output output. 15:03.620 --> 15:10.460 Run up put the sum of all the numbers from one up to and including the inputted number 15:13.420 --> 15:16.170 so we understand the problem first. 15:16.270 --> 15:23.060 We'll get a number from the user and then we'll loop from one up to that number. 15:25.270 --> 15:42.300 And create some from 1 to say and say so in is the number from the user. 15:42.430 --> 15:45.510 The user will input a number to us. 15:45.670 --> 15:52.050 So let's say the sum is something and the sum will start at zero. 15:52.060 --> 15:57.440 So we'll sign our new variable sum to be zero. 16:00.610 --> 16:14.390 Next he will say the from 1 to up to including. 16:14.990 --> 16:33.160 This is our stopping condition for stopping just like we have in problem 3. 16:33.240 --> 16:35.220 Then it's pretty simple. 16:35.460 --> 16:39.550 Say some is equal to 16:42.170 --> 16:42.840 never. 16:43.040 --> 16:46.220 Well for this we need again the 16:49.030 --> 16:52.850 hurt number and Boole's hurt never 16:56.290 --> 16:58.000 like we had in problem three. 16:58.110 --> 17:07.310 Some will be equal to some equals some plus the number. 17:07.350 --> 17:18.220 So whatever the sum was for just add the current number to this up and then sign that value back to 17:18.240 --> 17:23.800 some so we're just adding on CN to this every time. 17:24.000 --> 17:32.980 And those also didn't mention four but I'm indenting four and five here from three. 17:33.060 --> 17:41.280 This means that four and five are inside this loop so the loop only pertains to 4 and 5 steps sporran 17:41.320 --> 17:42.950 by. 17:43.070 --> 17:47.060 And this is important because in Step Five are outside the loop. 17:47.060 --> 17:48.380 Say we're done now. 17:49.240 --> 17:50.490 And then we'll say out. 17:50.560 --> 17:53.470 But some 17:57.250 --> 17:57.960 in that's it 18:01.020 --> 18:02.720 we're done with this. 18:02.860 --> 18:09.600 So I hope this is starting to set in a little bit bring you some more examples and in the next lecture 18:10.100 --> 18:13.770 to hopefully solidify what we've been learning so far.