self doubt

Question

The number of possible ordered Tree with 3 nodes A, B , C 

1. 16   b) 6   c) 12   d) 10

Comments

22 How??

 22 is not even in option. 

Did you see this https://gateoverflow.in/47181/number-of-ordered-trees

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It should be 30.

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i think we should have 12 trees...

how?

because we will have only two different types of trees of height =1 and 2 (all four trees will be considered as same if we put the values of a,b,c means they will be isomorphic)respectively...

and we can arrange them in 3! ways

so total ways = 2*3! = 12...

//this is my approach...