Questions tagged [disjoint-union]
55 questions
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Multithreaded union-find algorithm not working properly
I am trying to implement a multithreaded Union-Find algorithm as outlined in this paper (https://citeseerx.ist.psu.edu/viewdoc/download?oi=10.1.1.56.8354&rep=rep1&type=pdf).
Using this, I am trying to find out the number of connected components in…
Sayan Barrie Mccullum
- 115
- 5
0
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Representatives in Disjoint Set Union
The goal is to efficiently obtain representatives of every set. Obtaining the root as representative is better since it gives more information about the set; nodes are often augmented with properties of their subtrees.
For example, given the…
AustinBest
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Getting ambiguous error for Vector. How to Fix it?
#include
using namespace std;
const int N = 1e5 + 10;
vector parent(N);
vector rank(N); // size
void make(int v)
{
parent[v] = v;
rank[v] = 1;//"rank" is ambiguous
}
int find(int v)
{
if (v == parent[v])
…
Anish Kumar Mohanty
- 17
- 7
0
votes
1 answer
Returning the right number of islands using Union Find
I am solving a question on LeetCode.com called Number of Islands:
Given an m x n 2D binary grid grid which represents a map of '1's (land) and '0's (water), return the number of islands. An island is surrounded by water and is formed by connecting…
Someone
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0
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0 answers
Amortized complexity of the union operation
There are lots of sources about amortized complexity or union-find, quick-find operations but I couldn't find anything about the proof of single union operation complexity.
So, how can I prove that the amortized complexity of the union operation is…
0
votes
1 answer
Find() operation for disjoint sets using "Path Halving"
According to Disjoint-set_data_structure, In Union section, I have a problem understanding the implementation of Path Halving approach.
function Find(x)
while x.parent ≠ x
x.parent := x.parent.parent
x := x.parent
return x
My first…
hack3r-0m
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1 answer
Can this problem done without bfs or storing edges?
You are given an undirected connected graph with n nodes and n edges. Now Given two nodes a and b. find the number of edges that lies in path from a to b but are not part of cycle.
(as number of edges is n there will be a cycle for sure). Can this…
piyushnbali
- 35
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0
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2 answers
In Disjoint Set Union (D.S.U.), why do we make the smaller sized subset as the child of the larger sized subset while performing the union operation?
I recently came across D.S.U. and its applications on the tree.As i was solving the related problems, I got Time Limit Exceeded error in some so i read the tutorial again and there I found that an improvised version of the normal union is…
Yash Verma
- 461
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0
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1 answer
Disjoint set union implementation using c++
I am implementing Disjoint-Set Union by Rank and Path Compression in c++ according to the cp algorithm.But here I am getting an error reference to 'rank' is ambiguous . I have read many articles about this error but could not get any satisfactory…
user9857651
0
votes
2 answers
Why is my Union Find Disjoint Sets algo for this problem not passing all test cases?
Sample input:
1
3 2
1 2
2 3
First line = # of test cases
First number of second line = number of people
Second number of second line = number of friendships, F
Following F lines = the friendships
Output would be the size of the largest friend…
J. Doe
- 85
- 1
- 6
0
votes
1 answer
fastest way to merge duplicate cells in without looping Excel
I have cells containing duplicate values that i want to merge quickly. The table looks like this:
Sub MergeCells()
Application.DisplayAlerts = False
Dim n As Name
Dim fc As FormatCondition
Dim Rng As Range, R As Range
Dim lRow As Long
Dim I&,…
sifar
- 1,086
- 1
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- 43
0
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1 answer
How should Union operation in disjoint-set data structure properly implemented?
There are many different descriptions and examples for the disjoint-set structure available on-line.
In some cases, for each set, it stores "rank". When a set is merged into another set, the rank of the former is increased by 1, if they are of the…
user31264
- 6,557
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0
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1 answer
Graph Traversal count clouds [python]
Given a 2D grid skyMap composed of '1's (clouds) and '0's (clear sky), count the number of clouds.
A cloud is surrounded by clear sky, and is formed by connecting adjacent clouds horizontally or vertically. You can assume that all four edges of the…
aerin
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3 answers
Code to form a set from a list of element pairs in java
Say I have a list of pair of elements like (1, 2) (3, 4) where no duplicates are present and for a pair (p, q) p != q.
How to form a set from this elements using simple code (I do not intend to use a data structure like disjoint set and unions but…
Subhomoy Sikdar
- 526
- 5
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0
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1 answer
How to detect a cycle in an Undirected Graph using Disjoint Sets?
Algorithm:
For each edge (u, v) in the Adjacency list:
If u and v do not belong to the same set:
Union(u, v)
else:
return true // cycle detected
return false
Graph:
(1)-------(2)
Adjacency List:
[1] -> [2]
[2] -> [1]
Disjoint-Sets:
{{1},…
Abhishek
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