Problem 45303. Combinatorics - 01

Created by Asif Newaz

Solve Later

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<ul><li>Input=[x,n]</li><li>where x is an array of numbers(or strings) and n is a +ve number.</li></ul><p>for example, x=[1,2] and n=6.</p><p>The output will be a matrix containing all the possible permutations of the vector x having n elements(no of columns=n).
besides that -</p><ul><li>each row should contain equal number of occurance of the elements of x. (3 ones, 3 twos)</li><li>no initial segment can have more 2's than 1's. e.g. [2 2 1 2 1 1] - is invalid.since there are more 2's in the 1st appearance than 1's.</li></ul><ul><li>y=[</li></ul><pre>     1     1     1     2     2     2
     1     1     2     1     2     2
     1     1     2     2     1     2
     1     2     1     1     2     2
     1     2     1     2     1     2
     1     2     1     2     2     1
     2     1     1     1     2     2
     2     1     1     2     1     2
     2     1     1     2     2     1
     2     1     2     1     1     2
     2     1     2     1     2     1
     2     1     2     2     1     1
     2     2     1     1     1     2
     2     2     1     1     2     1
     2     2     2     1     1     1]</pre>

* Input=[x,n]
* where x is an array of numbers(or strings) and n is a +ve number.

for example, x=[1,2] and n=6.

The output will be a matrix containing all the possible permutations of the vector x having n elements(no of columns=n).
besides that -

* each row should contain equal number of occurance of the elements of x. (3 ones, 3 twos)
* no initial segment can have more 2's than 1's. e.g. [2 2 1 2 1 1] - is invalid.since there are more 2's in the 1st appearance than 1's.

* y=[

1     1     1     2     2     2
     1     1     2     1     2     2
     1     1     2     2     1     2
     1     2     1     1     2     2
     1     2     1     2     1     2
     1     2     1     2     2     1
     2     1     1     1     2     2
     2     1     1     2     1     2
     2     1     1     2     2     1
     2     1     2     1     1     2
     2     1     2     1     2     1
     2     1     2     2     1     1
     2     2     1     1     1     2
     2     2     1     1     2     1
     2     2     2     1     1     1]

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Solution Stats

4 Solutions
3 Solvers

Last Solution submitted on Apr 02, 2020

Last 200 Solutions

Problem Comments

3 Comments

3 Comments

Binbin Qi on 2 Apr 2020

I don't understand, can you explain the second rule?

Asif Newaz on 2 Apr 2020

all combinations of x & y of length n
1. they must appear n/2 times each
2. no initial segment of the string has more y's than x's
so, 'yyxyxx' -- the 2nd rule is broken here. since 1st appearance of x contains only one x while y [the second element] contains 2.

count (1stelement) >= count (2nd element) >= count (3rd element) ..
Hope this makes it clear

Binbin Qi on 2 Apr 2020

@Asif, thank you! I see.

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Problem Tags

combinatorics logic

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