From 939e357668010181e8507532c3976eeb47136afa Mon Sep 17 00:00:00 2001
From: that-ar-guy <mohdarahman124@gmail.com>
Date: Wed, 26 Feb 2025 15:54:13 +0530
Subject: [PATCH] added a star

---
 pysnippets/Path_Algoithms/a_star.py      | 41 ++++++++++++++++++++
 pysnippets/Path_Algoithms/test_a_star.py | 49 ++++++++++++++++++++++++
 2 files changed, 90 insertions(+)
 create mode 100644 pysnippets/Path_Algoithms/a_star.py
 create mode 100644 pysnippets/Path_Algoithms/test_a_star.py

diff --git a/pysnippets/Path_Algoithms/a_star.py b/pysnippets/Path_Algoithms/a_star.py
new file mode 100644
index 0000000..813c5dc
--- /dev/null
+++ b/pysnippets/Path_Algoithms/a_star.py
@@ -0,0 +1,41 @@
+from typing import Tuple, List, Dict
+from heapq import heappop, heappush
+import math
+from data_classes import Graph
+from logger_config import logger
+
+def heuristic(node: Tuple[int, int], goal: Tuple[int, int]) -> float:
+    """Euclidean distance heuristic."""
+    return math.sqrt((node[0] - goal[0])**2 + (node[1] - goal[1])**2)
+
+def a_star(graph: Graph, start: Tuple[int, int], end: Tuple[int, int]) -> Tuple[List[Tuple[int, int]], float]:
+    try:
+        open_set = []
+        heappush(open_set, (0, start))
+        g_score: Dict[Tuple[int, int], float] = {vertex: float('inf') for vertex in graph.vertices}
+        g_score[start] = 0
+        came_from: Dict[Tuple[int, int], Tuple[int, int]] = {}
+        
+        while open_set:
+            _, current = heappop(open_set)
+            
+            if current == end:
+                path = []
+                while current in came_from:
+                    path.insert(0, current)
+                    current = came_from[current]
+                path.insert(0, start)
+                return path, g_score[end]
+            
+            for neighbor, weight in graph.edges.get(current, {}).items():
+                tentative_g_score = g_score[current] + weight
+                if tentative_g_score < g_score[neighbor]:
+                    g_score[neighbor] = tentative_g_score
+                    f_score = tentative_g_score + heuristic(neighbor, end)
+                    heappush(open_set, (f_score, neighbor))
+                    came_from[neighbor] = current
+        
+        raise ValueError("Path not found")
+    except Exception as e:
+        logger.error(f"Error in A* algorithm: {e}")
+        raise
\ No newline at end of file
diff --git a/pysnippets/Path_Algoithms/test_a_star.py b/pysnippets/Path_Algoithms/test_a_star.py
new file mode 100644
index 0000000..99f78cd
--- /dev/null
+++ b/pysnippets/Path_Algoithms/test_a_star.py
@@ -0,0 +1,49 @@
+import unittest
+from data_classes import Graph
+from a_star import a_star
+import sys
+import os
+sys.path.insert(0, os.path.abspath(os.path.join(os.path.dirname(__file__), '..')))
+class TestAStar(unittest.TestCase):
+    def setUp(self):
+        vertices = {(0, 0), (1, 0), (1, 1), (2, 1), (2, 2)}
+        edges = {
+        (0, 0): {(1, 0): 1},
+        (1, 0): {(1, 1): 1, (0, 0): 1},
+        (1, 1): {(2, 1): 1, (1, 0): 1},
+        (2, 1): {(2, 2): 1, (1, 1): 1},
+        (2, 2): {(2, 1): 1}
+        }
+        self.graph = Graph(vertices, edges)
+        self.graph.vertices = {
+            (0, 0), (1, 0), (1, 1), (2, 1), (2, 2)
+        }
+        self.graph.edges = {
+            (0, 0): {(1, 0): 1},
+            (1, 0): {(1, 1): 1, (0, 0): 1},
+            (1, 1): {(2, 1): 1, (1, 0): 1},
+            (2, 1): {(2, 2): 1, (1, 1): 1},
+            (2, 2): {(2, 1): 1}
+        }
+    
+    def test_valid_path(self):
+        path, cost = a_star(self.graph, (0, 0), (2, 2))
+        self.assertEqual(path, [(0, 0), (1, 0), (1, 1), (2, 1), (2, 2)])
+        self.assertEqual(cost, 4)
+    
+    def test_no_path(self):
+        self.graph.edges = {
+            (0, 0): {(1, 0): 1},
+            (1, 0): {(0, 0): 1},
+            (2, 2): {}  # Disconnected node
+        }
+        with self.assertRaises(ValueError):
+            a_star(self.graph, (0, 0), (2, 2))
+    
+    def test_same_start_end(self):
+        path, cost = a_star(self.graph, (1, 1), (1, 1))
+        self.assertEqual(path, [(1, 1)])
+        self.assertEqual(cost, 0)
+
+if __name__ == "__main__":
+    unittest.main()
\ No newline at end of file