1
00:00:00,740 --> 00:00:02,240
Biton supports recursion.

2
00:00:02,270 --> 00:00:06,200
So how to write the recursive code in Python we shall be discussing here.

3
00:00:08,480 --> 00:00:09,460
What is recursion?

4
00:00:09,500 --> 00:00:16,430
So let me explain that one at first, the process in which a function calls itself directly or indirectly

5
00:00:16,640 --> 00:00:22,280
will be known as the recursion, and the corresponding function will be known as the recursive function.

6
00:00:22,610 --> 00:00:27,740
So that means what within the function body, the function will be called itself.

7
00:00:27,890 --> 00:00:33,080
So that is a direct calling and whatever the intended calling from the function and that function will

8
00:00:33,080 --> 00:00:33,590
be called.

9
00:00:33,740 --> 00:00:38,110
But that function in turn will be calling the the calling function.

10
00:00:38,240 --> 00:00:40,270
So that is known as the indirect recursion.

11
00:00:40,430 --> 00:00:46,010
So whatever the case, the recursion is there and the respective function is called recursive function.

12
00:00:47,240 --> 00:00:53,390
Using recursive algorithm, certain problems can be solved quite easily, and with the fewer number

13
00:00:53,390 --> 00:00:56,940
of calls in recursion, there will be a best guess.

14
00:00:57,110 --> 00:01:01,070
So what does a biscuit's that means in businesses for certain inputs?

15
00:01:01,370 --> 00:01:06,330
Outputs are known to us, and that is known as a business just considered in case of fact.

16
00:01:06,350 --> 00:01:07,340
Well, calculation.

17
00:01:07,490 --> 00:01:13,580
The best guess is that if the input number is zero or if the input number is one, then the factorial

18
00:01:13,580 --> 00:01:14,360
value will be one.

19
00:01:14,360 --> 00:01:22,250
So that is a Becka's say in the subject calculation of two numbers that Becka's is that if the two numbers

20
00:01:22,250 --> 00:01:26,540
are equal, then the city is any one of the number itself.

21
00:01:26,720 --> 00:01:28,550
So that is known as a best guess.

22
00:01:28,730 --> 00:01:31,490
That means for certain inputs, outputs unknown to us.

23
00:01:32,090 --> 00:01:34,460
So Python supports recursion.

24
00:01:36,350 --> 00:01:42,420
So advantages of recursion, recursive functions make the code look clean and elegant.

25
00:01:42,680 --> 00:01:48,980
We know that in our data structure we had two algorithms for your two hours of problem, and we know

26
00:01:48,980 --> 00:01:54,440
that in case of recursive algorithm, we we wrote only four to five statements that are putting some

27
00:01:54,440 --> 00:01:55,730
non recursive algorithm.

28
00:01:55,790 --> 00:01:58,220
We had to write one page full of codes.

29
00:01:58,430 --> 00:02:02,410
So that means that recursive algorithms are very easy to write.

30
00:02:02,540 --> 00:02:03,880
The future course are there.

31
00:02:04,040 --> 00:02:10,540
So obviously that programmers will feel comfortable environment to write a function in a recursive version.

32
00:02:11,180 --> 00:02:16,710
So a complex task can be broken down into simpler problems using recursion here.

33
00:02:17,180 --> 00:02:23,240
So second generation is easier with recursion than using some nested iterations.

34
00:02:23,900 --> 00:02:26,520
So now what are the disadvantages of recursion?

35
00:02:26,900 --> 00:02:30,650
Sometimes the logic behind recursion is hard to follow through.

36
00:02:30,770 --> 00:02:32,330
So that is a very important one.

37
00:02:32,360 --> 00:02:37,910
So while writing the recursive algorithm must be having a good grip over the programming logic, other

38
00:02:37,950 --> 00:02:42,920
than sometimes the recursive algorithm will become too much tricky for you to understand the logic.

39
00:02:43,370 --> 00:02:51,260
Recursive calls are expensive, Insaaf inefficient as they take up a loss of memory and time with the

40
00:02:51,260 --> 00:02:54,200
depth of recursion is too big.

41
00:02:54,320 --> 00:02:59,390
In that case, obviously it will go on keeping the instances of the previous coding.

42
00:02:59,420 --> 00:03:02,630
So that's why the use memory recommended will be there.

43
00:03:02,870 --> 00:03:09,560
And that's why there is a one of the disadvantages of using a one recursive algorithm and recursive

44
00:03:09,560 --> 00:03:11,810
functions are hard to debug.

45
00:03:12,110 --> 00:03:15,940
So these are the different advantages and disadvantages of recursion.

46
00:03:16,100 --> 00:03:21,260
So let us go for one practical demonstration where we'll be showing you that how this recursion can

47
00:03:21,260 --> 00:03:23,800
be implemented using python coding.

48
00:03:24,050 --> 00:03:25,760
So here is the demonstration for you.

49
00:03:26,270 --> 00:03:32,220
In this particular demonstration, we are going to discuss recursion, how to implement recursion here

50
00:03:32,220 --> 00:03:33,730
to a defined one method.

51
00:03:33,740 --> 00:03:40,190
The name of the method is fact, which is taking this in as input parameter, if any, is less than

52
00:03:40,190 --> 00:03:41,780
equal to one return one.

53
00:03:41,790 --> 00:03:47,450
We know that in case of recursion, there will be some Becka's that is for certain inputs outputs to

54
00:03:47,450 --> 00:03:48,190
be known to us.

55
00:03:48,200 --> 00:03:55,220
We know that if the value of any digital or the value of any one, then factorial of N will be one here.

56
00:03:55,790 --> 00:03:59,960
Other is what will happen, return and start factoring in minus one.

57
00:04:00,530 --> 00:04:05,540
So let us suppose we have this value five here so n will be assigned to five.

58
00:04:05,540 --> 00:04:08,740
Five is less than equal to one is false.

59
00:04:09,110 --> 00:04:12,020
So it will go for five in two factorial.

60
00:04:12,020 --> 00:04:17,610
For now, factorial force of four will be assigned to and four is less than equal to one.

61
00:04:17,630 --> 00:04:18,770
The condition is false.

62
00:04:18,950 --> 00:04:21,990
So to go for four in two factorial three.

63
00:04:22,340 --> 00:04:26,000
So again, in this case we'll be having three and two factorial.

64
00:04:26,000 --> 00:04:27,020
Two again.

65
00:04:27,030 --> 00:04:29,320
Two is less than equal to one condition is false.

66
00:04:29,320 --> 00:04:32,210
So it will go for two in two factorial.

67
00:04:32,210 --> 00:04:35,560
One and N is less than equal to one will be true.

68
00:04:35,570 --> 00:04:37,690
So it will be returning the value one here.

69
00:04:38,030 --> 00:04:41,240
So that is my factorial, one that will get multiplied with two.

70
00:04:41,900 --> 00:04:44,900
So I'll be getting two here so that will get multiplied with three.

71
00:04:44,930 --> 00:04:50,620
So now this particular recursive call will retries back to the through the columns.

72
00:04:50,720 --> 00:04:55,520
And ultimately I'm going to get this one that is five two factorial four.

73
00:04:55,790 --> 00:05:00,620
So Factorial four will be obtained as 14 to three to two into one.

74
00:05:00,920 --> 00:05:04,000
So that that will be our twenty four into five.

75
00:05:04,130 --> 00:05:05,950
So 128 will be the outcome.

76
00:05:06,200 --> 00:05:07,640
So let us go for the execution.

77
00:05:07,640 --> 00:05:11,190
You can find that the factor of five is 120.

78
00:05:11,540 --> 00:05:15,560
So in this way, the recursive function can be written in Python.

79
00:05:16,280 --> 00:05:17,510
Thanks for watching this video.