From 5ac7536c516bd04ba0959ef11db0aec7cd03186b Mon Sep 17 00:00:00 2001
From: Sanan507 <227714367+Sanan507@users.noreply.github.com>
Date: Mon, 3 Aug 2026 00:20:56 +0000
Subject: [PATCH] feat(pathfinding): Add Greedy Best-First Search Algorithm

---
 .../pathfinding/GreedyBFSModel.java           | 55 +++++++++++++++++++
 .../pathfinding/PathfindingFactory.java       | 10 +++-
 .../visualizer/utils/ComplexityCatalog.java   |  9 +++
 3 files changed, 73 insertions(+), 1 deletion(-)
 create mode 100644 backend/src/main/java/com/algorithmrace/visualizer/algorithms/pathfinding/GreedyBFSModel.java

diff --git a/backend/src/main/java/com/algorithmrace/visualizer/algorithms/pathfinding/GreedyBFSModel.java b/backend/src/main/java/com/algorithmrace/visualizer/algorithms/pathfinding/GreedyBFSModel.java
new file mode 100644
index 0000000..b64ff4f
--- /dev/null
+++ b/backend/src/main/java/com/algorithmrace/visualizer/algorithms/pathfinding/GreedyBFSModel.java
@@ -0,0 +1,55 @@
+package com.algorithmrace.visualizer.algorithms.pathfinding;
+
+import java.util.Comparator;
+import java.util.PriorityQueue;
+
+public class GreedyBFSModel extends PathfindingModel {
+  private final PriorityQueue<GridCell> openSet =
+      new PriorityQueue<>(Comparator.comparingDouble(c -> c.hCost));
+
+  public GreedyBFSModel() {
+    super("Greedy Best-First");
+  }
+
+  private double heuristic(GridCell a, GridCell b) {
+    return Math.abs(a.row - b.row) + Math.abs(a.col - b.col);
+  }
+
+  @Override
+  public void step() {
+    if (isDone() || openSet.isEmpty()) {
+      markDone();
+      return;
+    }
+    GridCell current = openSet.poll();
+    if (current == end) {
+      reconstructPath(end);
+      markDone();
+      return;
+    }
+    if (current.state != CellState.START) {
+      current.state = CellState.VISITED;
+    }
+    addStep();
+    for (GridCell nb : getNeighbors(current)) {
+      if (nb.state == CellState.EMPTY || nb.state == CellState.END) {
+        nb.hCost = heuristic(nb, end);
+        nb.parent = current;
+        if (nb.state == CellState.EMPTY) {
+          nb.state = CellState.FRONTIER;
+        }
+        openSet.add(nb);
+      }
+    }
+  }
+
+  @Override
+  public void reset() {
+    openSet.clear();
+    resetStats();
+    if (start != null) {
+      start.hCost = heuristic(start, end);
+      openSet.add(start);
+    }
+  }
+}
diff --git a/backend/src/main/java/com/algorithmrace/visualizer/algorithms/pathfinding/PathfindingFactory.java b/backend/src/main/java/com/algorithmrace/visualizer/algorithms/pathfinding/PathfindingFactory.java
index f2f38b8..54aac29 100644
--- a/backend/src/main/java/com/algorithmrace/visualizer/algorithms/pathfinding/PathfindingFactory.java
+++ b/backend/src/main/java/com/algorithmrace/visualizer/algorithms/pathfinding/PathfindingFactory.java
@@ -13,12 +13,20 @@ public static PathfindingModel create(String name) {
       case "A* Search" -> new AStarModel();
       case "Bellman-Ford" -> new BellmanFordModel();
       case "Bidirectional BFS" -> new BidirectionalBFSModel();
+      case "Greedy Best-First" -> new GreedyBFSModel();
       default ->
           throw new IllegalArgumentException("Unrecognized pathfinding algorithm requested.");
     };
   }
 
   public static List<String> allNames() {
-    return List.of("BFS", "DFS", "Dijkstra", "A* Search", "Bellman-Ford", "Bidirectional BFS");
+    return List.of(
+        "BFS",
+        "DFS",
+        "Dijkstra",
+        "A* Search",
+        "Bellman-Ford",
+        "Greedy Best-First",
+        "Bidirectional BFS");
   }
 }
diff --git a/backend/src/main/java/com/algorithmrace/visualizer/utils/ComplexityCatalog.java b/backend/src/main/java/com/algorithmrace/visualizer/utils/ComplexityCatalog.java
index 7bbf192..8f22f63 100644
--- a/backend/src/main/java/com/algorithmrace/visualizer/utils/ComplexityCatalog.java
+++ b/backend/src/main/java/com/algorithmrace/visualizer/utils/ComplexityCatalog.java
@@ -188,6 +188,15 @@ public final class ComplexityCatalog {
         "Combines travelled distance with a heuristic estimate to guide the search toward the"
             + " goal.",
         "choose lowest f = g + h\nrelax neighbors");
+    add(
+        "Greedy Best-First",
+        "O(b^m)",
+        "O(b^m)",
+        "O(b^m)",
+        "O(b^m)",
+        "Relies solely on a heuristic distance to the goal, providing a fast but non-optimal"
+            + " search.",
+        "choose lowest h\nrelax neighbors");
     add(
         "Bidirectional BFS",
         "O(b^(d/2))",