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package bipartitegraph
import . "github.com/onsi/gomega/matchers/support/goraph/node"
import . "github.com/onsi/gomega/matchers/support/goraph/edge"
import "github.com/onsi/gomega/matchers/support/goraph/util"
func (bg *BipartiteGraph) LargestMatching() (matching EdgeSet) {
paths := bg.maximalDisjointSLAPCollection(matching)
for len(paths) > 0 {
for _, path := range paths {
matching = matching.SymmetricDifference(path)
}
paths = bg.maximalDisjointSLAPCollection(matching)
}
return
}
func (bg *BipartiteGraph) maximalDisjointSLAPCollection(matching EdgeSet) (result []EdgeSet) {
guideLayers := bg.createSLAPGuideLayers(matching)
if len(guideLayers) == 0 {
return
}
used := make(map[Node]bool)
for _, u := range guideLayers[len(guideLayers)-1] {
slap, found := bg.findDisjointSLAP(u, matching, guideLayers, used)
if found {
for _, edge := range slap {
used[edge.Node1] = true
used[edge.Node2] = true
}
result = append(result, slap)
}
}
return
}
func (bg *BipartiteGraph) findDisjointSLAP(
start Node,
matching EdgeSet,
guideLayers []NodeOrderedSet,
used map[Node]bool,
) ([]Edge, bool) {
return bg.findDisjointSLAPHelper(start, EdgeSet{}, len(guideLayers)-1, matching, guideLayers, used)
}
func (bg *BipartiteGraph) findDisjointSLAPHelper(
currentNode Node,
currentSLAP EdgeSet,
currentLevel int,
matching EdgeSet,
guideLayers []NodeOrderedSet,
used map[Node]bool,
) (EdgeSet, bool) {
used[currentNode] = true
if currentLevel == 0 {
return currentSLAP, true
}
for _, nextNode := range guideLayers[currentLevel-1] {
if used[nextNode] {
continue
}
edge, found := bg.Edges.FindByNodes(currentNode, nextNode)
if !found {
continue
}
if matching.Contains(edge) == util.Odd(currentLevel) {
continue
}
currentSLAP = append(currentSLAP, edge)
slap, found := bg.findDisjointSLAPHelper(nextNode, currentSLAP, currentLevel-1, matching, guideLayers, used)
if found {
return slap, true
}
currentSLAP = currentSLAP[:len(currentSLAP)-1]
}
used[currentNode] = false
return nil, false
}
func (bg *BipartiteGraph) createSLAPGuideLayers(matching EdgeSet) (guideLayers []NodeOrderedSet) {
used := make(map[Node]bool)
currentLayer := NodeOrderedSet{}
for _, node := range bg.Left {
if matching.Free(node) {
used[node] = true
currentLayer = append(currentLayer, node)
}
}
if len(currentLayer) == 0 {
return []NodeOrderedSet{}
} else {
guideLayers = append(guideLayers, currentLayer)
}
done := false
for !done {
lastLayer := currentLayer
currentLayer = NodeOrderedSet{}
if util.Odd(len(guideLayers)) {
for _, leftNode := range lastLayer {
for _, rightNode := range bg.Right {
if used[rightNode] {
continue
}
edge, found := bg.Edges.FindByNodes(leftNode, rightNode)
if !found || matching.Contains(edge) {
continue
}
currentLayer = append(currentLayer, rightNode)
used[rightNode] = true
if matching.Free(rightNode) {
done = true
}
}
}
} else {
for _, rightNode := range lastLayer {
for _, leftNode := range bg.Left {
if used[leftNode] {
continue
}
edge, found := bg.Edges.FindByNodes(leftNode, rightNode)
if !found || !matching.Contains(edge) {
continue
}
currentLayer = append(currentLayer, leftNode)
used[leftNode] = true
}
}
}
if len(currentLayer) == 0 {
return []NodeOrderedSet{}
} else {
guideLayers = append(guideLayers, currentLayer)
}
}
return
}
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