Swift Prims algorithm
$begingroup$
Lots of Prims algorithm implementations seem long, and rely on a priority queue implementation.
If I use an adjacency matrix I can then calculate the next item to take using functional programming in Swift.
func prims (_ matrix : [[Int]]) {
var selected = 0
var selectedSoFar = Set<Int>()
selectedSoFar.insert( (matrix[selected].enumerated().min{ $0.element < $1.element }?.offset)! )
while selectedSoFar.count < matrix.count {
var minValue = Int.max
var minIndex = selected
var initialRow = 0
for row in selectedSoFar {
let candidateMin = matrix[row].enumerated().filter{$0.element > 0 && !selectedSoFar.contains($0.offset) }.min{ $0.element < $1.element }
if (minValue > candidateMin?.element ?? Int.max ) {
minValue = candidateMin?.element ?? Int.max
minIndex = (candidateMin?.offset) ?? 0
initialRow = row
}
}
print ("edge value (minValue) with (initialRow) to (minIndex)")
selectedSoFar.insert(minIndex)
selected = (minValue)
}
}
let input = [[0,9,75,0,0],[9,0,95,19,42],[75,95,0,51,66],[0,19,51,0,31],[0,42,66,31,0]]
prims(input)
Essentially is there anything "wrong" with this implementation? This is not homework, my code runs correctly for the included output and I appreciate this is faster if I use an adjacency matrix. However the Ray Wenderlich implementation of Prims uses 7 files and >200 lines of code. Am I missing something?
swift
asked 2 mins ago
WishIHadThreeGunsWishIHadThreeGuns
1
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$begingroup$
Lots of Prims algorithm implementations seem long, and rely on a priority queue implementation.
If I use an adjacency matrix I can then calculate the next item to take using functional programming in Swift.
func prims (_ matrix : [[Int]]) {
var selected = 0
var selectedSoFar = Set<Int>()
selectedSoFar.insert( (matrix[selected].enumerated().min{ $0.element < $1.element }?.offset)! )
while selectedSoFar.count < matrix.count {
var minValue = Int.max
var minIndex = selected
var initialRow = 0
for row in selectedSoFar {
let candidateMin = matrix[row].enumerated().filter{$0.element > 0 && !selectedSoFar.contains($0.offset) }.min{ $0.element < $1.element }
if (minValue > candidateMin?.element ?? Int.max ) {
minValue = candidateMin?.element ?? Int.max
minIndex = (candidateMin?.offset) ?? 0
initialRow = row
}
}
print ("edge value (minValue) with (initialRow) to (minIndex)")
selectedSoFar.insert(minIndex)
selected = (minValue)
}
}
let input = [[0,9,75,0,0],[9,0,95,19,42],[75,95,0,51,66],[0,19,51,0,31],[0,42,66,31,0]]
prims(input)
Essentially is there anything "wrong" with this implementation? This is not homework, my code runs correctly for the included output and I appreciate this is faster if I use an adjacency matrix. However the Ray Wenderlich implementation of Prims uses 7 files and >200 lines of code. Am I missing something?
swift
asked 2 mins ago
WishIHadThreeGunsWishIHadThreeGuns
1
New contributor
WishIHadThreeGuns is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$endgroup$
add a comment |
$begingroup$
Lots of Prims algorithm implementations seem long, and rely on a priority queue implementation.
If I use an adjacency matrix I can then calculate the next item to take using functional programming in Swift.
func prims (_ matrix : [[Int]]) {
var selected = 0
var selectedSoFar = Set<Int>()
selectedSoFar.insert( (matrix[selected].enumerated().min{ $0.element < $1.element }?.offset)! )
while selectedSoFar.count < matrix.count {
var minValue = Int.max
var minIndex = selected
var initialRow = 0
for row in selectedSoFar {
let candidateMin = matrix[row].enumerated().filter{$0.element > 0 && !selectedSoFar.contains($0.offset) }.min{ $0.element < $1.element }
if (minValue > candidateMin?.element ?? Int.max ) {
minValue = candidateMin?.element ?? Int.max
minIndex = (candidateMin?.offset) ?? 0
initialRow = row
}
}
print ("edge value (minValue) with (initialRow) to (minIndex)")
selectedSoFar.insert(minIndex)
selected = (minValue)
}
}
let input = [[0,9,75,0,0],[9,0,95,19,42],[75,95,0,51,66],[0,19,51,0,31],[0,42,66,31,0]]
prims(input)
Essentially is there anything "wrong" with this implementation? This is not homework, my code runs correctly for the included output and I appreciate this is faster if I use an adjacency matrix. However the Ray Wenderlich implementation of Prims uses 7 files and >200 lines of code. Am I missing something?
swift
asked 2 mins ago
WishIHadThreeGunsWishIHadThreeGuns
1
New contributor
WishIHadThreeGuns is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$endgroup$
Lots of Prims algorithm implementations seem long, and rely on a priority queue implementation.
If I use an adjacency matrix I can then calculate the next item to take using functional programming in Swift.
func prims (_ matrix : [[Int]]) {
var selected = 0
var selectedSoFar = Set<Int>()
selectedSoFar.insert( (matrix[selected].enumerated().min{ $0.element < $1.element }?.offset)! )
while selectedSoFar.count < matrix.count {
var minValue = Int.max
var minIndex = selected
var initialRow = 0
for row in selectedSoFar {
let candidateMin = matrix[row].enumerated().filter{$0.element > 0 && !selectedSoFar.contains($0.offset) }.min{ $0.element < $1.element }
if (minValue > candidateMin?.element ?? Int.max ) {
minValue = candidateMin?.element ?? Int.max
minIndex = (candidateMin?.offset) ?? 0
initialRow = row
}
}
print ("edge value (minValue) with (initialRow) to (minIndex)")
selectedSoFar.insert(minIndex)
selected = (minValue)
}
}
let input = [[0,9,75,0,0],[9,0,95,19,42],[75,95,0,51,66],[0,19,51,0,31],[0,42,66,31,0]]
prims(input)
Essentially is there anything "wrong" with this implementation? This is not homework, my code runs correctly for the included output and I appreciate this is faster if I use an adjacency matrix. However the Ray Wenderlich implementation of Prims uses 7 files and >200 lines of code. Am I missing something?
swift
swift
asked 2 mins ago
WishIHadThreeGunsWishIHadThreeGuns
1
New contributor
WishIHadThreeGuns is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 2 mins ago
WishIHadThreeGunsWishIHadThreeGuns
1
New contributor
WishIHadThreeGuns is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 2 mins ago
WishIHadThreeGunsWishIHadThreeGuns
1
New contributor
WishIHadThreeGuns is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 2 mins ago
WishIHadThreeGunsWishIHadThreeGuns
1
asked 2 mins ago
WishIHadThreeGunsWishIHadThreeGuns
1
1
New contributor
WishIHadThreeGuns is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
New contributor
WishIHadThreeGuns is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
WishIHadThreeGuns is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
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