From d44b0594576287299b5cc7bcd095009d5552dff7 Mon Sep 17 00:00:00 2001
From: Harrison <yunyangdeng@gmail.com>
Date: Tue, 21 Apr 2020 00:42:00 -0500
Subject: [PATCH] Changed DFS algorithm to use hashset.

---
 .../pathfinding/DepthFirstSearch.java         | 24 +++++++++----------
 1 file changed, 11 insertions(+), 13 deletions(-)

diff --git a/src/main/java/ca/recrown/islandsurvivalcraft/pathfinding/DepthFirstSearch.java b/src/main/java/ca/recrown/islandsurvivalcraft/pathfinding/DepthFirstSearch.java
index 236e199..f5edc1b 100644
--- a/src/main/java/ca/recrown/islandsurvivalcraft/pathfinding/DepthFirstSearch.java
+++ b/src/main/java/ca/recrown/islandsurvivalcraft/pathfinding/DepthFirstSearch.java
@@ -1,7 +1,8 @@
 package ca.recrown.islandsurvivalcraft.pathfinding;
 
-import java.util.ArrayList;
+import java.util.HashSet;
 import java.util.LinkedList;
+import java.util.Objects;
 import java.util.PriorityQueue;
 import java.util.Queue;
 
@@ -10,10 +11,10 @@ public class DepthFirstSearch {
     private CoordinateValidatable validatable;
     private Node startNode;
     private Node endNode;
-    private ArrayList<Node> checkedNodes;
+    private HashSet<Node> checkedNodes;
 
     public DepthFirstSearch() {
-        checkedNodes = new ArrayList<>();
+        checkedNodes = new HashSet<>();
     }
 
     public DepthFirstSearch(CoordinateValidatable validatable) {
@@ -62,7 +63,7 @@ public class DepthFirstSearch {
                 n.shallowCopyTo(endNode);
                 return true;
             }
-            if (!n.check()) {
+            if (checkedNodes.add(n)) {
                 for (int i = 0; i < n.child.length; i++) {
                     Node child = n.child[i];
                     if (validatable.validate(child.x, child.y)) {
@@ -97,7 +98,7 @@ public class DepthFirstSearch {
                 endNode = n;
                 return true;
             }
-            if (!n.check()) {
+            if (checkedNodes.add(n)) {
                 for (int i = 0; i < n.child.length; i++) {
                     Node child = n.child[i];
                     if (validatable.validate(child.x, child.y)) {
@@ -134,14 +135,6 @@ public class DepthFirstSearch {
             return distance;
         }
 
-        public boolean check() {
-            if (checkedNodes.contains(this)) {
-                return true;
-            }
-            checkedNodes.add(this);
-            return false;
-        }
-
         @Override
         public boolean equals(Object obj) {
             if (obj instanceof Node) {
@@ -153,6 +146,11 @@ public class DepthFirstSearch {
             return false;
         }
 
+        @Override
+        public int hashCode() {
+            return Objects.hash(x, y);
+        }
+
         public void shallowCopyTo(Node node) {
             node.child = this.child;
             node.parent = this.parent;