From 912d30b13ac1169c2491bea6134b883d7619b127 Mon Sep 17 00:00:00 2001
From: Shifa Maqsood <shifamaqsood7@gmail.com>
Date: Sat, 12 Oct 2024 16:50:36 +0530
Subject: [PATCH] Create A* Search-Algorithm.ts

add hacktoberfest label
---
 graph/A* Search-Algorithm.ts | 96 ++++++++++++++++++++++++++++++++++++
 1 file changed, 96 insertions(+)
 create mode 100644 graph/A* Search-Algorithm.ts

diff --git a/graph/A* Search-Algorithm.ts b/graph/A* Search-Algorithm.ts
new file mode 100644
index 00000000..884c6a3a
--- /dev/null
+++ b/graph/A* Search-Algorithm.ts	
@@ -0,0 +1,96 @@
+interface Node {
+    id: number;
+    g: number; // Cost from start to this node
+    h: number; // Heuristic cost from this node to target
+    f: number; // Total cost
+    parent?: Node; // Parent node for path reconstruction
+}
+
+class GraphAStar {
+    private adjList: Map<number, number[]>;
+
+    constructor() {
+        this.adjList = new Map();
+    }
+
+    addVertex(vertex: number) {
+        this.adjList.set(vertex, []);
+    }
+
+    addEdge(v1: number, v2: number) {
+        this.adjList.get(v1)?.push(v2);
+        this.adjList.get(v2)?.push(v1); // for undirected graph
+    }
+
+    heuristic(node: number, target: number): number {
+        // This is a placeholder heuristic; replace with an actual heuristic function
+        return Math.abs(target - node);
+    }
+
+    astar(start: number, target: number): number[] | null {
+        const openSet: Node[] = [];
+        const closedSet: Set<number> = new Set();
+
+        const startNode: Node = { id: start, g: 0, h: this.heuristic(start, target), f: 0 };
+        openSet.push(startNode);
+
+        while (openSet.length) {
+            // Get the node with the lowest f score
+            openSet.sort((a, b) => a.f - b.f);
+            const currentNode = openSet.shift()!;
+
+            if (currentNode.id === target) {
+                const path: number[] = [];
+                let temp: Node | undefined = currentNode;
+
+                while (temp) {
+                    path.push(temp.id);
+                    temp = temp.parent;
+                }
+
+                return path.reverse(); // Return reversed path
+            }
+
+            closedSet.add(currentNode.id);
+
+            const neighbors = this.adjList.get(currentNode.id) || [];
+            for (const neighborId of neighbors) {
+                if (closedSet.has(neighborId)) continue;
+
+                const gScore = currentNode.g + 1; // Assuming cost is 1 for each edge
+                const hScore = this.heuristic(neighborId, target);
+                const fScore = gScore + hScore;
+
+                const existingNodeIndex = openSet.findIndex(node => node.id === neighborId);
+                if (existingNodeIndex === -1 || fScore < openSet[existingNodeIndex].f) {
+                    const neighborNode: Node = {
+                        id: neighborId,
+                        g: gScore,
+                        h: hScore,
+                        f: fScore,
+                        parent: currentNode
+                    };
+
+                    if (existingNodeIndex === -1) {
+                        openSet.push(neighborNode);
+                    } else {
+                        openSet[existingNodeIndex] = neighborNode;
+                    }
+                }
+            }
+        }
+
+        return null; // No path found
+    }
+}
+
+// Example usage
+const graphAStar = new GraphAStar();
+graphAStar.addVertex(1);
+graphAStar.addVertex(2);
+graphAStar.addVertex(3);
+graphAStar.addVertex(4);
+graphAStar.addEdge(1, 2);
+graphAStar.addEdge(2, 3);
+graphAStar.addEdge(3, 4);
+console.log(graphAStar.astar(1, 4)); // Output: [1, 2, 3, 4]