/
graph.go
221 lines (176 loc) · 4.33 KB
/
graph.go
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package utils
import (
"math"
"slices"
)
type ConnectionMap[K comparable] map[K]map[K]int
func (cMap ConnectionMap[K]) Betweeness() map[K]float64 {
cb := make(map[K]float64)
cMap.brandes(func(n K, stack *Stack[K], p map[K][]K, delta, sigma map[K]float64) {
for stack.Len() > 0 {
w := stack.Pop()
for _, v := range p[w] {
delta[v] += sigma[v] / sigma[w] * (1 + delta[w])
}
if w != n {
if d := delta[w]; d != 0 {
cb[w] += d
}
}
}
})
return cb
}
func (cMap ConnectionMap[K]) EdgeBetweeness() map[K]map[K]float64 {
cb := make(map[K]map[K]float64)
cMap.brandes(func(n K, stack *Stack[K], p map[K][]K, delta, sigma map[K]float64) {
for stack.Len() != 0 {
w := stack.Pop()
for _, v := range p[w] {
c := sigma[v] / sigma[w] * (1 + delta[w])
if _, ok := cb[v]; !ok {
cb[v] = map[K]float64{}
}
cb[v][w] += c
delta[v] += c
}
}
})
return cb
}
func (cMap ConnectionMap[K]) brandes(accumulate func(n K, stack *Stack[K], p map[K][]K, delta, sigma map[K]float64)) {
// based off of gonum's implementation: https://github.com/gonum/gonum/blob/v0.14.0/graph/network/betweenness.go
p := make(map[K][]K, len(cMap))
sigma := make(map[K]float64, len(cMap))
d := make(map[K]int, len(cMap))
delta := make(map[K]float64, len(cMap))
queue := NewQueue[K]()
for n := range cMap {
stack := NewStack[K]()
// reset everything
for w := range cMap {
p[w] = p[w][:0]
sigma[w] = 0
d[w] = -1
}
sigma[n] = 1
d[n] = 0
queue.Push(n)
for queue.Len() > 0 {
v := queue.Pop()
stack.Push(v)
for neighbor := range cMap[v] {
// neighbor found for first time
if d[neighbor] < 0 {
queue.Push(neighbor)
d[neighbor] = d[v] + 1
}
// shortest path to neighbor from v
if d[neighbor] == d[v]+1 {
sigma[neighbor] += sigma[v]
p[neighbor] = append(p[neighbor], v)
}
}
}
for v := range cMap {
delta[v] = 0
}
accumulate(n, stack, p, delta, sigma)
}
}
func (cMap ConnectionMap[K]) Dijkstra(source K) (map[K]int, map[K]K) {
distances := make(map[K]int, len(cMap))
pq := NewPriorityQueue[K, int]()
prev := map[K]K{}
for vertex := range cMap {
distances[vertex] = math.MaxInt
}
distances[source] = 0
pq.Init(distances)
for pq.Len() > 0 {
curNode, curNodeDist := pq.Pop()
for neighbor, dist := range cMap[curNode] {
alt := curNodeDist + dist
if alt < distances[neighbor] {
distances[neighbor] = alt
pq.Update(neighbor, alt)
prev[neighbor] = curNode
}
}
}
return distances, prev
}
func (cMap ConnectionMap[K]) DijkstraWithDest(source K, destination K) int {
distances := make(map[K]int, len(cMap))
pq := NewPriorityQueue[K, int]()
for vertex := range cMap {
distances[vertex] = math.MaxInt
}
distances[source] = 0
for vertex, distance := range distances {
pq.Push(vertex, distance)
}
for pq.Len() > 0 {
curNode, curNodeDist := pq.Pop()
if curNode == destination {
break
}
for neighbor, dist := range cMap[curNode] {
alt := curNodeDist + dist
if alt < distances[neighbor] {
distances[neighbor] = alt
pq.Update(neighbor, alt)
}
}
}
return distances[destination]
}
func (cMap ConnectionMap[K]) LongestDijkstraWithDest(source K, destination K) (int, []K) {
distances := make(map[K]int, len(cMap))
pq := NewPriorityQueue[K, int]()
pq.SetPriorityOrder(true)
prev := map[K]K{}
for vertex := range cMap {
distances[vertex] = math.MinInt
}
distances[source] = 0
for vertex, distance := range distances {
pq.Push(vertex, distance)
}
for pq.Len() > 0 {
curNode, curNodeDist := pq.Pop()
for neighbor, dist := range cMap[curNode] {
if nodeIsAlreadyInPath(prev, curNode, neighbor) {
continue
}
alt := curNodeDist + dist
if alt > distances[neighbor] {
distances[neighbor] = alt
pq.Update(neighbor, alt)
prev[neighbor] = curNode
}
}
}
return distances[destination], reconstructPath(prev, source, destination)
}
func nodeIsAlreadyInPath[K comparable](prev map[K]K, source, node K) bool {
curNode := source
ok := true
for ok {
curNode, ok = prev[curNode]
if ok && curNode == node {
return true
}
}
return false
}
func reconstructPath[K comparable](prev map[K]K, source, dest K) []K {
path := []K{dest}
curNode := dest
for curNode != source {
curNode = prev[curNode]
path = append(path, curNode)
}
slices.Reverse(path)
return path
}