Questions tagged [greedy-algorithms]

An algorithm which at every point makes the locally optimal choice.

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Does the awards budget cut problem support a sub $O(n\log n)$ time solution?

There's a famous problem these days in the interview prep community (particularly in PRAMP) called the awards budget cut problem. The problem gives you an input of $n$ integers called grants $g_1 ... ...
-2
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1answer
56 views

Finding a greedy ordering criteria

I've been thinking through a problem, and I won't go into all the details here but I'm stumped on a particular subproblem: Consider this following definition of a task: $T_k = (a_k, b_k)$. $a_k$ is ...
5
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0answers
72 views

reference request: greedy algorithm for fractional interval covering

Reference Request I've found a natural greedy algorithm for the problem below. My question is: what is already known about fast algorithms for this problem (faster than general linear programming, ...
3
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1answer
170 views

Interval partitioning with restrictions: NP-complete or efficiently solvable?

The interval partitioning problem can be solved efficiently using a greedy algorithm. However, adding restrictions on the interval assignment to the problem results in a problem that appears harder. ...
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0answers
70 views

Are the intermediary sets in maximum cardinality search optimal in some way?

The maximum cardinality search (MCS) algorithm works as follows. Given a weighted graph $G = (V, E)$ where $w(u, v)$ denotes the weight of the edge $\{u, v\}$, we select a start node $a \in V$ and do ...
3
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1answer
251 views

Is this greedy algorithm for vertex cover studied before?

For the vertex cover problem (Given a graph $G$, find a minimum set $S$ of vertices such that $G - S$ is edgeless), there are two famous greedy algorithms. The edge greedy (finding an edge and taking ...
14
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1answer
467 views

Why is the Greedy Conjecture so difficult?

I recently learned about the Greedy conjecture for the Shortest Superstring Problem. In this problem, we are given a set of strings $s_1,\dots, s_n$ and we want to find the shortest superstring $s$ ...
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167 views

Simulate a heap in linear time

Is there anything in the literature on the following problem?: Take a sequence of operations of Insert(element) and PopMin and ...
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0answers
174 views

Which well-known algorithmic problem is this an instance of?

Consider that you have n counters initialised with numbers $M_1 \dots M_n$. In each round you decrement exactly $k$ out of these counters. Keep doing this until at least $n-k+1$ counters are zero, so ...
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0answers
84 views

Is it sufficient to only check on the vertices? Greedy algorithm

Suppose that I have a downwards closed Polyhedron and a vector $\omega$ and a greedy algorithm that goes as follows: Given an initial $x_0$, order the indices of $\omega$. Then for each $i$, solve $\...
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2answers
3k views

Dynamic Programming vs Greedy Algorithm

In (Sniedovich 2006) "Dijkstra's algorithm revisited: the dynamic programming connexion", Sniedovich provides us another interpretation of Dijkstra's algorithm as a dynamic programming implementation. ...
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1answer
544 views

Huffman Tree Depth, Is there any theory?

I'd like to as a variation on this question regarding Huffman tree building. Is there any theory or rule of thumb to calculate the depth of a Huffman tree from the input (or frequency), without ...
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2answers
622 views

Packing $n$ objects into $m$ bins whose size is variable

Assume we have $n$ fixed size objects with sizes $O_1$ to $O_n$. Also, assume we have $m$ bins with size $a \times B_1$ to $a \times B_m$ in which $a$ is a real number and $a\ge1$. We want to put ...
3
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1answer
386 views

What is the reverse of greedy algorithm for setcover?

A common approach to approximating SETCOVER is the greedy algorithm (Algorithm 2.2 Vazirani). This algorithm greedily picks the most cost-effective subset at each iteration, removes covered elements, ...
14
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1answer
2k views

What greedy algorithm satisfies greedy choice property but does not have optimal substructure?

Based on the textbook Introduction to Algorithms, the correctness of a greedy algorithm requires a problem to have two properties: greedy choice property optimal substructure It is easy to come up ...
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357 views

How good is greedy in average?

Given a family ${\cal F}\subset 2^E$ of (feasible solutions), the maximization problem on ${\cal F}$ is, for every weighting $x:E\to \{0,1,\ldots\}$ of ground elements, to compute the maximum weight ...
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0answers
296 views

Algorithm to merge two incomplete sequences of symbols (strings) into a complete one

I initially considered this problem trivial, but then looked with more attention, I could not find an easy solution. Let's say we have two ordered lists of symbols (strings): ...
15
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3answers
2k views

Does every greedy algorithm have matroid structure?

It is well established that for every matroid $M$ and any weight function $w$, there exits an algorithm $\mbox{GreedyBasis}(M,w)$ which returns a maximum weight basis of $M$. So, is the reverse ...
21
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2answers
925 views

Max-Cut algorithm that shouldn't work, unclear why

OK, this might seem like a homework question and, in a sense, it is. As a homework assignment in an undergraduate algorithms class, I gave the following classic: Given an undirected graph $G=(V,E)$, ...
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0answers
418 views

Worst case of heuristics for symmetric TSP

I have implemented the nearest neighbor heuristic for solving symmetric TSP problems. I was wondering if there is any relation between the solution found by the heuristic and the optimal solution? ...
0
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1answer
170 views

Planning jobs as partition problem

I think this should be a famous problem but I could not find its name. I have $n$ jobs with size $s_i$ that are offered at time $t_i$ and $k$ machines. How can I assign jobs to machines to minimize ...
3
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2answers
575 views

Follow-the-leader algorithm in swarm formation: literature on the subject?

In an AI strategy game simulation, I devised an algorithm for forming a group and swarming a known location without communication among soldiers (ie. every individual agent makes a locally optimum ...
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0answers
858 views

Pure Greedy algorithms

I study pure greedy algorithms in different bases. I am interested in the following question: Is there such a Riesz basis $D$ in Hilbert space and $f\in H$ such that $$ \|f-G_m(f,D)\| > Cm^{-...
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88 views

Partitioning based on distribution

Having a set of numbers $S={s_i}$, I want to assign them to bins, $b_i$, such that the sum of items on bins follow a specific distribution. For two bins and uniform distribution, this problem is ...
7
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1answer
407 views

expected number of sets generated by greedy set cover ?

I see most of the analysis for the greedy set cover analyses the approximation ratio. However, assume that each element in $T$ belong with a constant probability to one of the sets of $S$ (where $S = \...
3
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3answers
5k views

Complexity of greedy coloring

I was looking at some heuristics for coloring and found this book on Google books: Graph Colorings By Marek Kubale They describe the Greedy algorithm as follows: ...
10
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3answers
852 views

Is it possible to prove that, for a given problem, no optimal greedy algorithms exist?

Greedy is a non-formal term, but it could be (not sure, that's why I'm asking) that for certain problems, greediness can be mathematically formulated and thus be proven that no optimal greedy ...
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0answers
137 views

How to prove $k^{n-1}, k^{n-2}, \ldots, k^0$ will result with minimum number of coins? [closed]

I am not sure how to prove or disprove for $A_n = \{k^{n-1}, k^{n-2}, \ldots, k^0\}$ for some $k > 1$, the greedy method will yield solutions with minimum number of coins. I know that each number ...
38
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9answers
4k views

Optimal greedy algorithms for NP-hard problems

Greed, for lack of a better word, is good. One of the first algorithmic paradigms taught in introductory algorithms course is the greedy approach. Greedy approach results in simple and intuitive ...