Initial Commit

Author: chitholian

.gitignore

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+.vscode
+

LICENSE.txt

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README.md

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+
+# Some Search Techniques in Artificial Intelligence
+
+This repository is a part of the Lab assignments of the course **CSE 714** (Artifical Intelligence Lab).
+
+Here, I tried to implement some Search Algorithms (in Python 3.7.3) including:
+
+- Breadth First Search
+- Depth First Search
+- Uniform Cost Search
+- Depth Limited Search
+- Iterative Deepening Search
+- Bi-Directional Search
+- Best First Search
+- Greedy Search
+- A* Search
+- Iterative Deepening A*

astar.py

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+#    Copyright 2019 Atikur Rahman Chitholian
+#
+#    Licensed under the Apache License, Version 2.0 (the "License");
+#    you may not use this file except in compliance with the License.
+#    You may obtain a copy of the License at
+#
+#        http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS,
+#    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#    See the License for the specific language governing permissions and
+#    limitations under the License.
+
+from queue import heappop, heappush
+from math import inf
+
+class Graph:
+    def __init__(self, directed=True):
+        self.edges = {}
+        self.huristics = {}
+        self.directed = directed
+
+    def add_edge(self, node1, node2, cost = 1, __reversed=False):
+        try: neighbors = self.edges[node1]
+        except KeyError: neighbors = {}
+        neighbors[node2] = cost
+        self.edges[node1] = neighbors
+        if not self.directed and not __reversed: self.add_edge(node2, node1, True)
+
+    def set_huristics(self, huristics={}):
+        self.huristics = huristics
+
+    def neighbors(self, node):
+        try: return self.edges[node]
+        except KeyError: return []
+
+    def cost(self, node1, node2):
+        try: return self.edges[node1][node2]
+        except: return inf
+
+
+    def a_star_search(self, start, goal):
+        found, fringe, visited, came_from, cost_so_far = False, [(self.huristics[start], start)], set([start]), {start: None}, {start: 0}
+        print('{:11s} | {}'.format('Expand Node', 'Fringe'))
+        print('--------------------')
+        print('{:11s} | {}'.format('-', str(fringe[0])))
+        while not found and len(fringe):
+            _, current = heappop(fringe)
+            print('{:11s}'.format(current), end=' | ')
+            if current == goal: found = True; break
+            for node in self.neighbors(current):
+                new_cost = cost_so_far[current] + self.cost(current, node)
+                if node not in visited or cost_so_far[node] > new_cost:
+                    visited.add(node); came_from[node] = current; cost_so_far[node] = new_cost
+                    heappush(fringe, (new_cost + self.huristics[node], node))
+            print(', '.join([str(n) for n in fringe]))
+        if found: print(); return came_from, cost_so_far[goal]
+        else: print('No path from {} to {}'.format(start, goal)); return None, inf
+
+    @staticmethod
+    def print_path(came_from, goal):
+        parent = came_from[goal]
+        if parent:
+            Graph.print_path(came_from, parent)
+        else: print(goal, end='');return
+        print(' =>', goal, end='')
+
+
+    def __str__(self):
+        return str(self.edges)
+
+graph = Graph(directed=True)
+graph.add_edge('A', 'B', 4)
+graph.add_edge('A', 'C', 1)
+graph.add_edge('B', 'D', 3)
+graph.add_edge('B', 'E', 8)
+graph.add_edge('C', 'C', 0)
+graph.add_edge('C', 'D', 7)
+graph.add_edge('C', 'F', 6)
+graph.add_edge('D', 'C', 2)
+graph.add_edge('D', 'E', 4)
+graph.add_edge('E', 'G', 2)
+graph.add_edge('F', 'G', 8)
+graph.set_huristics({'A': 8, 'B': 8, 'C': 6, 'D': 5, 'E': 1, 'F': 4, 'G': 0})
+start, goal = 'A', 'G'
+traced_path, cost = graph.a_star_search(start, goal)
+if (traced_path): print('Path:', end=' '); Graph.print_path(traced_path, goal); print('\nCost:', cost)

bds.py

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+#    Copyright 2019 Atikur Rahman Chitholian
+#
+#    Licensed under the Apache License, Version 2.0 (the "License");
+#    you may not use this file except in compliance with the License.
+#    You may obtain a copy of the License at
+#
+#        http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS,
+#    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#    See the License for the specific language governing permissions and
+#    limitations under the License.
+
+from collections import deque
+
+class Graph:
+    def __init__(self, directed=True):
+        self.edges = {}
+        self.directed = directed
+
+    def add_edge(self, node1, node2, __reversed=False):
+        try: neighbors = self.edges[node1]
+        except KeyError: neighbors = set()
+        neighbors.add(node2)
+        self.edges[node1] = neighbors
+        if not self.directed and not __reversed: self.add_edge(node2, node1, True)
+
+    def neighbors(self, node):
+        try: return self.edges[node]
+        except KeyError: return []
+
+    def bi_directional_search(self, start, goal):
+        found, fringe1, visited1, came_from1 = False, deque([start]), set([start]), {start: None}
+        meet, fringe2, visited2, came_from2 = None, deque([goal]), set([goal]), {goal: None}
+        while not found and (len(fringe1) or len(fringe2)):
+            print('FringeStart: {:30s} | FringeGoal: {}'.format(str(fringe1), str(fringe2)))
+            if len(fringe1):
+                current1 = fringe1.pop()
+                if current1 in visited2: meet = current1; found = True; break
+                for node in self.neighbors(current1):
+                    if node not in visited1: visited1.add(node); fringe1.appendleft(node); came_from1[node] = current1
+            if len(fringe2):
+                current2 = fringe2.pop()
+                if current2 in visited1: meet = current2; found = True; break
+                for node in self.neighbors(current2):
+                    if node not in visited2: visited2.add(node); fringe2.appendleft(node); came_from2[node] = current2
+        if found: print(); return came_from1, came_from2, meet
+        else: print('No path between {} and {}'.format(start, goal)); return None, None, None
+
+    @staticmethod
+    def print_path(came_from, goal):
+        parent = came_from[goal]
+        if parent:
+            Graph.print_path(came_from, parent)
+        else: print(goal, end='');return
+        print(' =>', goal, end='')
+
+    def __str__(self):
+        return str(self.edges)
+
+
+graph = Graph(directed=False)
+graph.add_edge('A', 'B'); graph.add_edge('A', 'S'); graph.add_edge('S', 'G')
+graph.add_edge('S', 'C'); graph.add_edge('C', 'F'); graph.add_edge('G', 'F')
+graph.add_edge('C', 'D'); graph.add_edge('C', 'E'); graph.add_edge('E', 'H')
+graph.add_edge('G', 'H')
+start, goal = 'A', 'H'
+traced_path1, traced_path2, meet = graph.bi_directional_search(start, goal)
+if meet:
+    print('Meeting Node:', meet)
+    print('Path From Start:', end=' '); Graph.print_path(traced_path1, meet); print()
+    print('Path From Goal:', end=' '); Graph.print_path(traced_path2, meet); print()