Minimum weight cycle in an undirected weighted graph in scala
Scala program for Minimum weight cycle in an undirected weighted graph. Here more information.
/*
Scala program for
Minimum weight cycle in an undirected graph
*/
class AjlistNode(
// Vertices node key
var id: Int,
var weight: Int,
var next: AjlistNode)
{
def this(id: Int, weight: Int)
{
// Set value of node key
this(id, weight, null);
}
}
class Vertices(var data: Int,
var next: AjlistNode,
var last: AjlistNode)
{
def this(data: Int)
{
this(data, null, null);
}
}
class Graph(
// Number of Vertices
var size: Int,
var result: Int,
var node: Array[Vertices])
{
def this(size: Int)
{
// Set value
this(size, 0, Array.fill[Vertices](size)(null));
this.setData()
}
// Set initial node value
def setData(): Unit = {
if (size <= 0)
{
println("\nEmpty Graph");
}
else
{
var index: Int = 0;
while (index < size)
{
// Set initial node value
node(index) = new Vertices(index);
index += 1;
}
}
}
def connection(start: Int, last: Int, weight: Int): Unit = {
// Safe connection
var edge: AjlistNode = new AjlistNode(last, weight);
if (node(start).next == null)
{
node(start).next = edge;
}
else
{
// Add edge at the end
node(start).last.next = edge;
}
// Get last edge
node(start).last = edge;
}
// Handling the request of adding new edge
def addEdge(start: Int, last: Int, weight: Int): Unit = {
if (start >= 0 && start < this.size &&
last >= 0 && last < this.size)
{
// Connect edge with weight
this.connection(start, last, weight);
this.connection(last, start, weight);
}
else
{
// When invalid nodes
print("\nNode missing (" + start + " " + last + ")");
}
}
def printGraph(): Unit = {
if (size > 0)
{
var index: Int = 0;
// Print graph ajlist
while (index < size)
{
print("\nAdjacency list of vertex " + index + " :");
var edge: AjlistNode = node(index).next;
while (edge != null)
{
// Display graph node value and weight
print(" " + node(edge.id).data + "[" + edge.weight + "]");
// Visit to next edge
edge = edge.next;
}
index += 1;
}
}
}
def minimumCycle(start: Int, last: Int,
visit: Array[Boolean], sum: Int,
length: Int): Unit = {
if (start >= this.size || last >= this.size ||
start < 0 || last < 0 || this.size <= 0)
{
return;
}
if (visit(start) == true)
{
// Here length are indicate loop length
if (length > 2 && start == last && sum < this.result)
{
// Here length is indicate number of nodes
// Because graph is undirected so we consider all cycle
// Which contains more than 2 node
// ---------------------
// When find a new min weight cycle
this.result = sum;
}
return;
}
// Here modified the value of visited node
visit(start) = true;
// This is used to iterate nodes edges
var edge: AjlistNode = node(start).next;
while (edge != null)
{
// Find solution using recursion
minimumCycle(edge.id, last, visit,
sum + (edge.weight), length + 1);
// Visit to next edge
edge = edge.next;
}
// Reset the value of visited node status
visit(start) = false;
}
def minWeightCycle(): Unit = {
if (this.size <= 0)
{
// Empty graph
return;
}
// Auxiliary space which is used to store
// information about visited node
// Set initial visited node status
var visit: Array[Boolean] = Array.fill[Boolean](this.size)(false);
this.result = Int.MaxValue;
var i: Int = 0;
while (i < size)
{
// Check cycle of node i to i
// Here initial cycle weight is zero
minimumCycle(i, i, visit, 0, 0);
i += 1;
}
// Display result
println("\nMin weight cycle : " + this.result);
}
}
object Main
{
def main(args: Array[String]): Unit = {
// 6 implies the number of nodes in graph
var g: Graph = new Graph(6);
// Connect node with an edge
// First and second parameter indicate node
// Last parameter is indicate weight
g.addEdge(0, 1, 3);
g.addEdge(0, 3, -3);
g.addEdge(0, 4, 7);
g.addEdge(0, 5, 1);
g.addEdge(1, 2, 11);
g.addEdge(1, 4, 8);
g.addEdge(2, 3, 1);
g.addEdge(2, 5, 4);
g.addEdge(3, 4, 2);
g.addEdge(4, 5, 8);
g.addEdge(5, 1, 0);
// Print graph element
g.printGraph();
// Test
g.minWeightCycle();
}
}
Output
Adjacency list of vertex 0 : 1[3] 3[-3] 4[7] 5[1]
Adjacency list of vertex 1 : 0[3] 2[11] 4[8] 5[0]
Adjacency list of vertex 2 : 1[11] 3[1] 5[4]
Adjacency list of vertex 3 : 0[-3] 2[1] 4[2]
Adjacency list of vertex 4 : 0[7] 1[8] 3[2] 5[8]
Adjacency list of vertex 5 : 0[1] 2[4] 4[8] 1[0]
Min weight cycle : 3
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