Flow Network Algorithm
In graph theory, a flow network (also known as a transportation network) is a directed graph where each edge has a capacity and each edge receives a flow. A network can be used to model traffic in a computer network, circulation with demands, fluids in pipes, currents in an electrical circuit, or anything like in which something travels through a network of nodes.
package org.gs.digraph
import scala.collection.mutable.ListBuffer
/** Network with capacity and flow
*
* @constructor creates a new FlowNetwork with a vertex count
* @param v number of vertices
* @see [[https://algs4.cs.princeton.edu/64maxflow/FlowNetwork.java.html]]
* @author Scala translation by Gary Struthers from Java by Robert Sedgewick and Kevin Wayne.
*/
class FlowNetwork(val v: Int) {
require(v >= 0, s"Number of vertices, v:$v must be nonnegative")
private var _e = 0
private val _adj = Array.fill[List[FlowEdge]](v)(List[FlowEdge]())
def e(): Double = _e
def addEdge(e: FlowEdge): Unit = {
val _v = e.from
val w = e.to
def rangeGuard(x: Int): Boolean = x match {
case x if 0 until v contains x => true
case _ => false
}
require(rangeGuard(_v) && rangeGuard(w), s"verticies v:${_v} w:$w not in 0..$v ")
_adj(_v) = e :: _adj(_v)
_adj(w) = e :: _adj(w)
_e += 1
}
def adj(v: Int): List[FlowEdge] = _adj(v)
def edges(): Seq[FlowEdge] = for {
vV <- 0 until v
e <- adj(vV)
} yield e
override def toString(): String = {
val lf = sys.props("line.separator")
val sb = new StringBuilder()
sb append (s"$v ${_e} $lf")
def addLines(v: Int) {
sb append (s"$v : ")
adj(v) foreach (e => if(e.to != v) sb append (s"$e "))
}
for(vV <- 0 until v) addLines(vV)
sb.toString
}
}
