solved ancestor problem

projects/ancestor/ancestor.py

@@ -1,3 +1,55 @@
 
 def earliest_ancestor(ancestors, starting_node):
-    pass
+
+    # my graph will be set to a dictionary
+    my_graph = {}
+
+    # loop over over the list
+    for pair in ancestors:
+        # check if the key exist an
+        if pair[1] not in my_graph:
+            my_graph[pair[1]] = [pair[0]]
+        else:
+            my_graph[pair[1]].append(pair[0])
+    # if the key isn't in the list then its a parent node
+    if starting_node not in my_graph:
+        return -1
+
+    #initialzing my my with the starting node
+    my_stack = [(my_graph[starting_node], [starting_node])]
+    max_length = []
+
+    while len(my_stack) > 0:
+
+        # popping off the the path and parent nodes from the stack
+        current_node, path = my_stack.pop(0)
+
+        if len(current_node) > 0:
+
+            # loping over neighbors and adding them to the stack
+            for neighbor in current_node:
+
+                # adding neighbor to the path
+                my_path = path + [neighbor]
+
+                # if the neigh isnt in the graph then its a parent and that the end of the tree
+                if neighbor not in my_graph:
+
+                    # checking to see if the current path is longer
+                    if len(my_path) > len(max_length):
+                        max_length = my_path
+
+                    # Because they are equal, we need to compare the last element
+                    elif len(my_path) == len(max_length):
+                        if my_path[-1] < max_length[-1]:
+                            max_length = my_path
+
+                # the node has parents and we need to evaluate them       
+                else:
+                    my_stack.append((my_graph[neighbor], my_path))
+
+    return max_length[-1]
+
+
+if __name__ == '__main__':
+    print(earliest_ancestor([(1, 3), (2, 3), (3, 6), (5, 6), (5, 7), (4, 5), (4, 8), (8, 9), (11, 8), (10, 1)], 6))