From 192cda5257e2ff22ee2045467b179731fba027b3 Mon Sep 17 00:00:00 2001
From: Rohan Sircar <rohansircar@tuta.io>
Date: Fri, 3 Apr 2020 13:46:34 +0530
Subject: [PATCH] Added prim's algorithm and adjacency matrix

---
 src/main/scala/Main.scala | 84 ++++++++++++++++++++++++++++++++++++++-
 1 file changed, 83 insertions(+), 1 deletion(-)

diff --git a/src/main/scala/Main.scala b/src/main/scala/Main.scala
index 8209be7..06d0bb2 100644
--- a/src/main/scala/Main.scala
+++ b/src/main/scala/Main.scala
@@ -1,6 +1,7 @@
 import model.Coord
 import model.Customer
 import model.HHCEdge
+import scala.collection.mutable._
 object Main {
   def main(args: Array[String]): Unit = {
 
@@ -15,6 +16,7 @@ object Main {
 
     val cust3 = Customer(Coord(3, 5), 6)
     val cust4 = Customer(Coord(6, 8), 9)
+    val cust5 = Customer(Coord(5, 4), 6)
 
     val edge1 = HHCEdge(cust1, cust2)
     val edge2 = HHCEdge(cust3, cust4)
@@ -22,11 +24,91 @@ object Main {
     println(s"Edge 1 = ${edge1}")
     println(s"Edge 1 weight = ${edge1.weight}")
 
-    val V = Array(cust1, cust2, cust3, cust4)
+    val V = Array(cust1, cust2, cust3, cust4, cust5)
+
     val E = Array(edge1, edge2)
 
     V.foreach(println(_))
+    // prints
+    // Customer(Coord(3, 4), 5)
+    // Customer(Coord(2, 5), 7)
+    // Customer(Coord(3, 5), 6)
+    // Customer(Coord(6, 8), 9)
+    // Customer(Coord(5, 4), 6)
     E.foreach(println(_))
+    //prints
+    // HHCEdge(Customer(Coord(3, 4), 5), Customer(Coord(2, 5), 7))
+    // HHCEdge(Customer(Coord(3, 5), 6), Customer(Coord(6, 8), 9))
+
+    // sample adjacency
+    // format: off
+    val edges = Array(
+        Array(0 , 9 , 75, 0 , 0),
+        Array(9 , 0 , 95, 19, 42),
+        Array(75, 95, 0 , 51, 66),
+        Array(0 , 19, 51, 0 , 31),
+        Array(0 , 42, 66, 31, 0)
+    );
+
+    //format: on
+
+    // Prim's algorithm
+
+    val selected: ArrayBuffer[Boolean] =
+      ArrayBuffer.from(Array.ofDim[Boolean](5).toIndexedSeq)
+
+    selected(0) = true
+
+    var numberOfEdges = 0
+
+    for (_ <- numberOfEdges to 3) {
+      var min = 999999
+      var x = 0
+      var y = 0
+      for (i <- 0 to 4) {
+        if (selected(i) == true) {
+          for (j <- 0 to 4) {
+            if (selected(j) == false && edges(i)(j) != 0) {
+              if (min > edges(i)(j)) {
+                min = edges(i)(j)
+                x = i
+                y = j
+              }
+            }
+          }
+        }
+      }
+      println(s"Edge selected $x - $y : ${edges(x)(y)}")
+      selected(y) = true
+    }
+
+    // Prim's algorithm result
+    // Edge selected 0 - 1: 9
+    // Edge selected 1 - 3: 19
+    // Edge selected 3 - 4: 31
+    // Edge selected 3 - 2: 51
+
+    // Verify the result with the one at https://www.programiz.com/dsa/prim-algorithm
+
+    val edges2: ArrayBuffer[ArrayBuffer[Double]] = ArrayBuffer.empty
+
+    // create adjacency matrix from given customers
+    for (i <- 0 to 4) {
+      edges2.append(ArrayBuffer.empty)
+      for (j <- 0 to 4) {
+        edges2(i).append(HHCEdge(V(i), V(j)).weight)
+      }
+    }
+
+    println(edges2) // prints adjacency matrix
+
+    // ArrayBuffer(
+    //   ArrayBuffer(0.0               , 1.4142135623730951, 1.0              , 5.0              , 2.0),
+    //   ArrayBuffer(1.4142135623730951, 0.0               , 1.0              , 5.0              , 3.1622776601683795),
+    //   ArrayBuffer(1.0               , 1.0               , 0.0              , 4.242640687119285, 2.23606797749979),
+    //   ArrayBuffer(5.0               , 5.0               , 4.242640687119285, 0.0              , 4.123105625617661),
+    //   ArrayBuffer(2.0               , 3.1622776601683795, 2.23606797749979 , 4.123105625617661, 0.0),
+    // )
 
   }
 }