# Questions tagged [induction]

Questions about mathematical induction and inductive proofs.

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### on coq: Why is the proof complete after proving only for one induction when we have more than one variable?

So I'm learning coq. And I came across the proof for associativity in addition forall (a b c : nat) Appearntly when we do ...
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### Proving building a balanced BST out of sorted array is $\Theta(n)$

I'm having hard time proving building a balanced BST out of sorted array is $\Theta(n)$ I got the following formula: $$T(n)=2T(\frac{n}{2})+\Theta(1)$$ I tried to prove it by induction but got stuck ...
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### Prove by induction that the recurrence form of bubble sort is $\Omega(n^2)$

The recurrence form of bubble sort is $T(n)=T(n-1)+ n- 1$ How can I prove by induction that this is $\Omega(n^2)$? I'm stuck with $T(n+1) \geq cn^2 + n = n(cn+1)$
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### Given a tournament with $2^n$ vertices, show that there is a sub-tournament with at least $n + 1$ vertices that is acyclic

So a tournament is just a complete directed graph, I believe. I'm having trouble proving this problem. I know it is induction however. I was thinking the base case is $2^1$ vertices, and therefore ...
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### When can the coinduction hypothesis be used?

We can use the induction hypothesis when we are proving a property for a structure that is well-ordered. I am aware that there is a proof for this. When it comes to coinduction, I'm confused. One of ...
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### Prove that a red-black tree with $n$ internal nodes has height at most $2\lg(n+1)$

I cannot understand the first paragraph of the proof, which comes from the known book Introduction to Algorithms, third-edition, and I consider it has some errors, could anyone help me check about it? ...
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### Proving that $S^* = (S^*)^*$

I am going through some past exam paper questions on regular languages for some revision, and I am having a bit of trouble with converting general ideas into formal mathematical proofs. The question ...
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### Induction pitfalls with O notation and recursion

I read the following in CLRS 3rd Ed: I'm not sure I understand exactly how to avoid this pitfall. How would one know that the $\mathcal{O}$ notation in this case grows with $n$ and is thus not ...
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### Which inductive schemes can encode the following Agda definition?

Which induction schemes (e.g. induction-recursion by Dybjer and Setzer, "Irish" induction-recursion by McBride or induction-induction by Forsberg and Setzer or perhaps some simpler ones) allow one to ...
332 views

### Induction to prove equivalence of a recursive and iterative algorithm for Towers of Hanoi

Using induction how do you prove that two algorithm implementations, one recursive and the other iterative, of the Towers of Hanoi perform identical move operations? The implementations are as follows....
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### How do I approach inductive design problems with no information or context given?

As a starting point for our course in Artificial Intelligence, we are being taught induction. We received a number of homework assignments where we have to show our inductive approach for a given ...
206 views

### solving a problem with induction

The original question is the following prove that $2·\sum_{i=0}^{n-1} 3^{i} = 3^n-1$ for all n $\geq$ 1 I know that I have to prove by induction and have successfully done the base case, my IH is ...
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### What is induction-induction?

What is induction-induction? The resources I found are: the HoTT book, at the end of chapter 5.7. nLab's article a paper called Inductive-inductive definitions this blog post also mentions inductive-...
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### Deriving recursive definition from function specification

Given this function specification, where name xs is bound to a list, # denotes its cardinality and ...
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### Hanoi towers recursive expression for EVERY algorithm

What the recursive algorithm for moving $n$ disks says, is: If $n > 1$, move $n-1$ discs from A to B. Move the $n$th disk from A to C. If $n > 1$, move $n-1$ discs from B to C. Let $T_n$ be ...
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### Induction proof given recurrence of algorithm

I am having trouble starting this proof and wanted some clarification. Here are the details given: ...
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### Using induction prove that a K-SAT problem is NP-Complete

Using induction on k, how do I prove that the K-SAT problem is NP-complete? On wikipedia, it describes the Cook-Levin theorem to prove that K-SAT is NPC by reducting the K-SAT problem to a circuit-...
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### Prove grade-school multiplication algorithm applied to binary numbers

I want to prove that the basic multiplication algorithm is correct when applied to binary numbers. I try to follow the steps described here and here but didn't succeed. The basic implementation ...
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### Rules for consistency with mutual inductive families?

I'm trying to use a proof assistant to define a type and a relation that are mutually dependent on each other: ...
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### Is this proof of the map fusion law correct?

I am reading Functional Programming in Scala, where I have been asked to prove the map fusion law. Since Scala is what I am familiar with, I am using as my notation a kind of pseudo-Scala. Here is ...
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### dfa subtract multiple of 3 [duplicate]

Define a function 𝑑𝑖𝑓𝑓 ∈{0,1}→ℤ so: for everything w ∈{0,1}, diff w = # of 1's in w- # of 0's in w. Thus: 𝑑𝑖𝑓𝑓 𝜀=0; 𝑑𝑖𝑓𝑓 0=−1; 𝑑𝑖𝑓𝑓 0=−1; Let 𝐿 = {𝑤∈ {0,1} * | 𝑑𝑖𝑓𝑓 𝑤 = 3𝑚 ...
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### How to prove even with structural induction, for expression

E::= zero|two|expression + expression|expression*expression, E element of expression how do i prove E to be even. I have no clue on how to go about tackling this.
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### How to prove that a string is made up of subsequences occurring some arbitrary number of times using concatenation?

How to prove that a string, s is made up of n > 1 subsequences occurring some arbitrary number of times using concatenation ...
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### Induction on typing derivation in refinement types system

From the text Principles of Type Refinement page 14: The author introduces in definition 2.2.7 the rule: $$\dfrac{\Pi \vdash t : R \qquad R \le S}{\Pi \vdash t : S}$$ and gives the following ...
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### Proving the correctness of a square summing algorithm

int sumHelper(int n, int a) { if (n==0) return a; else return sumHelper(n-1, a + n*n); } int sumSqr(int n) { return sumHelper(n, 0); } I am supposed ...
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### Is Loop Invariant Proof a form of Induction?

As far as I see, what computer scientists refer to as loop invariant proofs are exact replicas of induction proof. Is it true? Can I state that loop invariant proof implies an induction? Is there a ...
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### Proving time-complexity analysis for merge-sort-like algorihtm

I have this algorithm, which is exactly like merge-sort, but instead of halving the array each recursion, it actually splits it into $1/4$ and $3/4$ parts. Other then that, it does exactly the same ...