feat: bfs algorithm

search.py

@@ -118,7 +118,36 @@ def depthFirstSearch(problem: SearchProblem):
 def breadthFirstSearch(problem: SearchProblem):
     """Search the shallowest nodes in the search tree first."""
     "*** YOUR CODE HERE ***"
-    util.raiseNotDefined()
+    actions = []
+
+    curr_state = problem.getStartState()
+    isGoal = problem.isGoalState(curr_state)
+
+    visited = set()
+    queue = util.Queue()
+
+    while not isGoal:
+        # push in the Stack
+        successors = problem.getSuccessors(curr_state)
+        for (state, direction, cost) in successors:
+            if state not in visited:
+                visited.add(state)
+                queue.push({
+                    'state': (state, direction, cost),
+                    'actions': actions
+                })
+
+        # check whether reachable
+        if queue.isEmpty():
+            return []
+        else:
+            obj = queue.pop()
+            (curr_state, direction, cost) = obj['state']
+            actions = obj['actions'] + [ direction ]
+            isGoal = problem.isGoalState(curr_state)
+
+    return actions
+    
 
 def uniformCostSearch(problem: SearchProblem):
     """Search the node of least total cost first."""