NguyenMichelle Graphs - Graph Exercises

graphs/possible_bipartition.py

@@ -1,5 +1,6 @@
 # Can be used for BFS
 from collections import deque 
+# doubly ended queue > list because append and pop are O(1)
 
 def possible_bipartition(dislikes):
     """ Will return True or False if the given graph
@@ -8,5 +9,102 @@ def possible_bipartition(dislikes):
         Time Complexity: ?
         Space Complexity: ?
     """
-    pass
+    pen_a = set()
+    pen_b = set()
+
+    # I referenced the solutions shared by Sid and Jen
+    # during Thursdays at Ada and read GeekForGeeks to
+    # supplement my understanding of the solution
+
+    # if the the list is empty
+    if not dislikes:
+        return True
+
+    # indexes represent whether or not nodes have been visited
+    visited = [False] * len(dislikes)
+
+    q = deque()
+    # add first index to q/deque
+    # q=([0])
+    q.append(0)
+
+    # while there is a value in the deque
+    while q:
+
+        # popleft() used to delete an argument from left end of deque
+        # current = 0
+        current = q.popleft()
+
+        # mark node as visited in initial list
+        visited[current] = True
+
+        # does current dog have dislikes?
+        # go to dislikes to read nested list at index 0
+        if not dislikes[current]:
+            # if no disikes, add 1 (next index) to deque
+            q.append(current+1)
+
+        # otherwise, for every dog in this nested list of dislikes
+        for dog in dislikes[current]:
+
+            # if node has not been visited append to deque
+            # meaning, that index will read False
+            if not visited[dog]:
+                # add to deque
+                q.append(dog)
+
+            # if dog (we are placing) is not in pen_a
+            if current not in pen_a:
+
+                # if enemy-dog is in pen_b
+                if dog in pen_b:
+                    return False
+
+                # add enemy-dog to pen_a
+                pen_a.add(dog)
+
+            else:
+
+                # if enemy-dog is in pen_a
+                if dog in pen_a:
+                    return False
+
+                # add enemy-dog to pen_b
+                pen_b.add(dog)
+
+    return True
+
+
+
+    # for dog_index in range(len(dislikes)):
+
+    #     print("PEN A: ", dog_index, " - ", pen_a)
+    #     print("PEN B: ", dog_index, " - ",  pen_b)
+
+    #     danger_in_a = False
+    #     danger_in_b = False
+
+    #     for enemy in dislikes[dog_index]:
+
+    #         if enemy in pen_a:
+    #             danger_in_a = True
+    #         elif enemy in pen_b:
+    #             danger_in_b = True
+
+    #     if danger_in_a == False:
+    #         pen_a.add(dog_index)
+    #     elif danger_in_b == False:
+    #         pen_b.add(dog_index)
+    #     else:
+    #         return False
+
+    #     print("PEN A: ", pen_a)
+    #     print("PEN B: ", pen_b)
+    #     print()
+
+    # return True
+
+
+
+