# Questions tagged [probabilistic-algorithms]

Questions about (typically randomized) algorithms that can produce no or an incorrect answer with a certain probability.

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### Probability of loss using a binary symmetric channel

Today we talked about Information Theory and the binary symetric channel. For newbies here is a little explanation : For instance if I want to send a binary to someone : The bit will be "flipped&...
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### Populating a vector of numbers to expose an error in a function implementation

So lets say I'm writing an algorithm that takes a vector as input. I want to know that I'm writing this algorithm correctly however so I of course write tests to see if the output equals what I expect ...
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### Distributional error probability of deterministic algorithm implies error probability of randomized algorithm?

Consider some problem $P$ and let's assume we sample the problem instance u.a.r. from some set $I$. Let $p$ be a lower bound on the distributional error of a deterministic algorithm on $I$, i.e., ...
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### Hash function, $h(k) = \lfloor km \rfloor$ is simple uniform for real $k$ independently, uniformly distributed in the range $0 \leq k < 1$

I was going through the text Introduction to Algorithms by Cormen et. al. where I came across the following statement: If the keys are known to be random real numbers $k$ independently and uniformly ...
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### Confusion about the Hiring Problem

I'm confused about where the probability from the hiring problem comes from. For background: We interview one person everyday who has a quality characteristic, x, from 0 to 1(distributed uniformly). ...
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### Why Convolutional codes is easy to factor/handle the uncertainty of a bit being a 0 or a 1 into the decoding?

Here is an excerpt from Andrew S. Tanenbaum, Computer Networks, 5th edition, Chapter 3 (The data link layer), Page 208: My question is about this part. [Convolutional codes have been popular in ...
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### What is an example of a Monte-Carlo algorithm for finding a Hamiltonian path?

I've recently been made aware that there exist Monte-Carlo algorithm(s?) for determining whether a Hamiltonian path exists in a graph. I am struggling to figure out how it would work. What is the ...
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### Reference on PCP theorem

Can someone recommend a reference on the PCP theorem that explains how it works via examples rather than formal CS language? Specifically, I'm looking for the example on how graph colouring can be ...
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### Hashing algorithm which minimizes distribution

Consider applications A1, A2 .. AN having properties P11, P12,... PN1, PN2.. Also consider buckets ...
48 views

### Sizing a Cuckoo filter for a subset of elements

Question I am considering the use of Cuckoo filter for a business case. To simplify the explanation here is an analogy of my needs: There are over $n = 30 000$ first names that exists in the whole ...
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### $k$-coloring in BPP, implies $k$-coloring in ZPP

Consider the next problem: $k$-COL: Given a graph $G=(V,E)$, does it have a valid $k$-coloring? I need to prove that if $k$-COL is in BPP, then it is also in ZPP. In other words, show that if there ...
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### Is there a complexity class QPP?

The complexity class PP is not considered tractable, because the probability of success can get arbitrarily close to 50% from above as the problem instances get larger, so that (e.g. if this approach ...
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### Recover a matrix with minimum number of queries

Alice has a matrix $A \in \{0,1\}^{n \times m}$ such that the sum of each row is $1$. Bob tries to find the indices of the ones (he knows that the sum of each row is $1$). The type of questions Bob ...
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### Probability of terminating in a state in a probabilistic algorithm

Suppose i have a circular array of $n$ elements. At time $t=0$ i am in position 0 of the array. The algorithm moves left or right with probability $p=1/2$ (since the array is circular when it moves ...
31 views

### Demonstrating that probability for every possible result is uniform at the end of an algorithm

I have memory of $k$ elements that you can imagine being represented by an array. One by one, the array receives a value corresponding to the time index, for example at $t=1$ the value will be $1$. At ...
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### Chernoff Bounds (upper tail)

For the proof of Chernoff Bounds (upper tail) we suppose δ<2e−1 . Like in this paper ([see this link ]) 1. Can you tell me why ?
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### Prove an estimator

Consider an undirected graph $G=(V,E)$ representing the social network of friendship/trust between students. We would like to form teams of three students that know each other. The question is to ...
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### Find expectation and calculate Chernoff bound [duplicate]

We have a group of employees and their company will assign a prize to as many employees as possible by finding the ones probably better than the rest. The company assigned the same 2 tasks to every ...
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### Find expectation with Chernoff bound

We have a group of employees and their company will assign a prize to as many employees as possible by finding the ones probably better than the rest. The company assigned the same $2$ tasks to every ...
573 views

### Derandomization of vertex cover algorithm

I have the following randomized-algorithm for the vertex cover problem. Let $B_0$ be the output set: Fix some order $e_1, e_2,...,e_m$ over all edges in the edge set E of G, and set $B_0=∅$. Add to ...
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### Grover's algorithm on probabilistic classical machines

As a starting point for this question, I came across this question, which AIUI is citing a construction showing how to simulate quantum circuits with a $PP$ algorithm, i.e. implying quantum ...
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### Predicting the outcome of sporting events with multiplicative scoring

In the Olympic format for sport climbing, eight athletes compete in three rounds of climbing. Their final score is the multiplication of their rankings in each round. For example, an athlete who comes ...
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### Understanding simulated annealing information theoretically

So I recently rediscovered simulated annealing though a path that others seem to be well aware of. I was aware of Metropolis-Hastings as a sampling algorithm that creates a Markov-Chain who's ...
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### What is the probability that an expanding bipartite graph exists with the property, |V1|=|V2|?

I want to find a bound on the above problem, and show that a random graph has a positive probability of being an expanding bipartite with the property, |V1|=|V2|. I am not getting, where should I ...
105 views

### Why an error probability of 1/3 in BPP?

BPP is defined as the class of polynomial-time random algorithms which have an error probability of at most 1/3. But why was 1/3 chosen? If we have an algorithm with some error probability less than ...
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### Are there efficient probabilistic multiplication algorithms that use O(n log n) gates?

Recently Harvey and Hoeven published a paper proving that integer multiplication can be performed using at most O(n log n) operations. This algorithm is theoretically interesting, but in practice ...