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/*
* Copyright © 2017-2018 AT&T Intellectual Property.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.onap.ccsdk.apps.controllerblueprints.core.utils
import java.util.*
/**
*
*
* @author Brinda Santh
*/
class TopologicalSortingUtils<V> {
private val neighbors: MutableMap<V, MutableList<V>> = hashMapOf()
val isDag: Boolean
get() = topSort() != null
override fun toString(): String {
val s = StringBuffer()
for (v in neighbors.keys)
s.append("\n " + v + " -> " + neighbors[v])
return s.toString()
}
fun getNeighbors(): Map<V, List<V>> {
return neighbors
}
fun add(vertex: V) {
if (neighbors.containsKey(vertex))
return
neighbors[vertex] = arrayListOf()
}
operator fun contains(vertex: V): Boolean {
return neighbors.containsKey(vertex)
}
fun add(from: V, to: V) {
this.add(from)
this.add(to)
neighbors[from]?.add(to)
}
fun remove(from: V, to: V) {
if (!(this.contains(from) && this.contains(to)))
throw IllegalArgumentException("Nonexistent vertex")
neighbors[from]?.remove(to)
}
fun outDegree(): Map<V, Int> {
val result: MutableMap<V, Int> = hashMapOf()
for (v in neighbors.keys)
result[v] = neighbors[v]!!.size
return result
}
fun inDegree(): MutableMap<V, Int> {
val result = HashMap<V, Int>()
for (v in neighbors.keys)
result[v] = 0 // All in-degrees are 0
for (from in neighbors.keys) {
for (to in neighbors[from]!!) {
result[to] = result[to]!! + 1 // Increment in-degree
}
}
return result
}
fun topSort(): List<V>? {
val degree = inDegree()
// Determine all vertices with zero in-degree
val zeroVerts = Stack<V>() // Stack as good as any here
for (v in degree.keys) {
if (degree[v] == 0) zeroVerts.push(v)
}
// Determine the topological order
val result = ArrayList<V>()
while (!zeroVerts.isEmpty()) {
val v = zeroVerts.pop() // Choose a vertex with zero in-degree
result.add(v) // Vertex v is next in topol order
// "Remove" vertex v by updating its neighbors
for (neighbor in neighbors[v]!!) {
degree[neighbor] = degree[neighbor]!! - 1
// Remember any vertices that now have zero in-degree
if (degree[neighbor] == 0) zeroVerts.push(neighbor)
}
}
// Check that we have used the entire graph (if not, there was a cycle)
return if (result.size != neighbors.size) null else result
}
fun bfsDistance(start: V): Map<*, *> {
val distance: MutableMap<V, Int> = hashMapOf()
// Initially, all distance are infinity, except start node
for (v in neighbors.keys)
distance[v] = -1
distance[start] = 0
// Process nodes in queue order
val queue = LinkedList<V>()
queue.offer(start) // Place start node in queue
while (!queue.isEmpty()) {
val v = queue.remove()
val vDist = distance[v]!!
// Update neighbors
for (neighbor in neighbors[v]!!) {
if (distance[neighbor] != null) continue // Ignore if already done
distance[neighbor] = vDist + 1
queue.offer(neighbor)
}
}
return distance
}
}
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