Which of the following is true in a tree: $E=O(V^2)$ or $E=O(V)$?











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I am doing a computer science assignment.



In the assignment, I was asked to find an algorithm with time complexity $O(|E|)$. The input is a connected acyclic graph (a free tree). I have come up with an algorithm costs $O(V^2)$.



I am thinking of whether the time complexity of my algorithm satisfy the requirement or not. Because I know that in a complete graph, $E = O(V^2)$. However, in this question, I am dealing with a tree with $V-1$ edges. So the question is which of the following is true in a tree: $E=O(V^2)$ or $E=O(V)$?










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  • That's the wrong question, because $O(V) subset O(V^2)$. It could be fixed by using $Theta$ instead of $O$.
    – Peter Taylor
    Nov 23 at 6:25















up vote
0
down vote

favorite












I am doing a computer science assignment.



In the assignment, I was asked to find an algorithm with time complexity $O(|E|)$. The input is a connected acyclic graph (a free tree). I have come up with an algorithm costs $O(V^2)$.



I am thinking of whether the time complexity of my algorithm satisfy the requirement or not. Because I know that in a complete graph, $E = O(V^2)$. However, in this question, I am dealing with a tree with $V-1$ edges. So the question is which of the following is true in a tree: $E=O(V^2)$ or $E=O(V)$?










share|cite|improve this question
























  • That's the wrong question, because $O(V) subset O(V^2)$. It could be fixed by using $Theta$ instead of $O$.
    – Peter Taylor
    Nov 23 at 6:25













up vote
0
down vote

favorite









up vote
0
down vote

favorite











I am doing a computer science assignment.



In the assignment, I was asked to find an algorithm with time complexity $O(|E|)$. The input is a connected acyclic graph (a free tree). I have come up with an algorithm costs $O(V^2)$.



I am thinking of whether the time complexity of my algorithm satisfy the requirement or not. Because I know that in a complete graph, $E = O(V^2)$. However, in this question, I am dealing with a tree with $V-1$ edges. So the question is which of the following is true in a tree: $E=O(V^2)$ or $E=O(V)$?










share|cite|improve this question















I am doing a computer science assignment.



In the assignment, I was asked to find an algorithm with time complexity $O(|E|)$. The input is a connected acyclic graph (a free tree). I have come up with an algorithm costs $O(V^2)$.



I am thinking of whether the time complexity of my algorithm satisfy the requirement or not. Because I know that in a complete graph, $E = O(V^2)$. However, in this question, I am dealing with a tree with $V-1$ edges. So the question is which of the following is true in a tree: $E=O(V^2)$ or $E=O(V)$?







graph-theory






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edited Nov 23 at 4:32









user302797

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19.7k92252










asked Nov 22 at 12:59









Billy Cheung

61




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  • That's the wrong question, because $O(V) subset O(V^2)$. It could be fixed by using $Theta$ instead of $O$.
    – Peter Taylor
    Nov 23 at 6:25


















  • That's the wrong question, because $O(V) subset O(V^2)$. It could be fixed by using $Theta$ instead of $O$.
    – Peter Taylor
    Nov 23 at 6:25
















That's the wrong question, because $O(V) subset O(V^2)$. It could be fixed by using $Theta$ instead of $O$.
– Peter Taylor
Nov 23 at 6:25




That's the wrong question, because $O(V) subset O(V^2)$. It could be fixed by using $Theta$ instead of $O$.
– Peter Taylor
Nov 23 at 6:25










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It is not. As you said $|E| = |V| - 1$ here. Hence, if your algorithm is in $O(|V|^2)$ it is not satisfied $O(|E|)$ here.






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    1 Answer
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    It is not. As you said $|E| = |V| - 1$ here. Hence, if your algorithm is in $O(|V|^2)$ it is not satisfied $O(|E|)$ here.






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      It is not. As you said $|E| = |V| - 1$ here. Hence, if your algorithm is in $O(|V|^2)$ it is not satisfied $O(|E|)$ here.






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        It is not. As you said $|E| = |V| - 1$ here. Hence, if your algorithm is in $O(|V|^2)$ it is not satisfied $O(|E|)$ here.






        share|cite|improve this answer












        It is not. As you said $|E| = |V| - 1$ here. Hence, if your algorithm is in $O(|V|^2)$ it is not satisfied $O(|E|)$ here.







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        share|cite|improve this answer










        answered Nov 22 at 14:27









        OmG

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