[ASSIGNMENT] 👉👉👉 ENVELOPE 📧 & LETTER 💌

Question

U have to find number of ways in which no letter goes to correct envelope
example ::: if input is 3
then , 3 envelope E1,E2,E3
3 letters L1,L2,L3
//correct combination ::: (E1L1 , E2L2 , E3L3)
👉 possible arrangements
(E1L2 , E2L3 , E3L1)
(E1L3 , E2L1 , E3L2)
/*therefore 2 such combinations for 3 letters and 3 envelopes such that no letter goes in correct envelope*/
//output must be 2

Bonus ::: print the combinations 🙌

all languages are welcome ☺

//best of luck & happy coding ☺👍

Answer 1

no@J.G.
I mean none of the letter goes to correct envelope , so there are some combinations which u need to exclude
/*even if 1 letter goes to correct envelope , then u have to remove that combination*/

//thats interesting ... right ? ☺

Answer 2

this whole is 1st combination ::: (E1L2 , E2L3 , E3L1)
this whole is 2nd comvination ::: (E1L3 , E2L1 , E3L2)
//so 2 combinations

//read the description carefully ☺ & try again 👍👍👍👍

/*I'll tell mathematical answer soon*/

Answer 3

here is some brief explanation on it
input : 3 //3 letters , 3 envelopes
output : 2

//how output comes as 2 , for what combinations ? 👇
1) total no. of combinations we can make is 3! = 6
(ie no. of ways of 3 letters in 3 envelope .... {1 letter in 1 envelope , u can't put 2 or more letters in 1 envelope} )
envelopes are E1,E2,E3 ... letters are L1,L2,L3
E1 is correct envelope for letter L1 , similarily ... E2 for L2 & E3 for L3

now we have to find no. of ways in which all letters are putted into envelopes but none of those letters goes in correct envelopes ... ie L1 doesn't go into E1 , L2 doesn't goes into E2 & L3 doesn't goes into E3
a) (E1L2 , E2L3 , E3L1)
b) (E1L3 , E2L1 , E3L2)
//2 combination possible ... ie a) and b)
as U can see in a)
that E1 holds L2 ... not L1 ,
E2 holds L3 ... not L2
E3 holds L1 ... not L3

//will mark best answer soon , after some more answers ☺👍

INPUT :::::
3

OUTPUT ::::
2
(E1L2 , E2L3 , E3L1)
(E1L3 , E2L1 , E3L2)

Answer 4

upto now , correct answers are of :::
Danigamy ,
Cpasgrave ,
DT ,
Pedro Demingos ,
Vadim Sukhotin ,
swim ,
Chloe

//U can check out their codes and understand what to output ☺

Answer 5

thats incorrect
/*see the correct codes & compare what should be the output for what input*/

Answer 6

mathematical soln
let u have n letters & U have to put them into n envelopes such that 1 letter goes into 1 envelope ,
then no. of ways such that none of the letter goes to right envelope , then U must substract those ways in which letter(s) goes to correct envelope
ie n! - {nC1.(n-1)! - nC2. (n-2)! + nC3. (n-3)! - ..... +(-1)^n.nCn.0!}
=n! (1/2! - 1/3! + 1/4! +.....+((-1)^n)/n!)

//hope u got it @Sreejith

Answer 7

Here's my try..:-
https://code.sololearn.com/chDBM2QhNn0q/?ref=app

Answer 8

So, what you're saying is:
If the user inputs x, the output should be every combination except {L1E1, L2E2, ... LXEX}?

Answer 9

A little too long, but there it goes:

https://code.sololearn.com/cjq5z97Ua6hU/#py

Answer 10

Just one little line of code:
https://code.sololearn.com/cwk3ef1iYAf6/?ref=app

Answer 11

My try in python..
https://code.sololearn.com/cT252pKw3UIt/?ref=app

Answer 12

Bonus part here:
https://code.sololearn.com/cM6AD4wkYOT5/?ref=app

Answer 13

Hope it works
https://code.sololearn.com/cPpuZbA7aywv/?ref=app

Answer 14

Here's my try:
edit: following the rules and corrected name, working on grouping

https://code.sololearn.com/cWE9s1StLzk0/?ref=app

Answer 15

My lazy brute force python:

https://code.sololearn.com/cP85OqQCXBRA/#py

1 letter and 1 envelope - 0 possible ways to completely fail the mailing
2 letters and 2 envelopes - 1 possible way to completely fail the mailing
3 l&e - 2 p
4 l&e - 9 p
5 l&e - 44 p
6 l&e - 265 p
7 l&e - 1854 p
8 l&e - 14833 p
9 l&e - 133496 p

Answer 16

https://code.sololearn.com/cPxFf4mZS6QJ/?ref=app

I get the same as the sample, but in 3 groups of 2; does this make my results incorrect?

Answer 17

I have better results and can match the sample. My solution is incomplete for n>3.

https://code.sololearn.com/cmWFNQm6mXoR/?ref=app

Answer 18

my try in python

https://code.sololearn.com/c5w9kO74n1RK/?ref=app

Answer 19

and please explain 5=44

factorial of 5(n) is 120
square of n is 25
factorial of n-1 is 24
square of n-1 is 16
n*(n-1) is 20
square of n*(n-1) is 400

even if you do this
120-25-24-16-5(same combination ) = 50

i can't get it
a bit explanation would be good

Answer 20

https://code.sololearn.com/cuSUwbJE2c66/?ref=app