diff --git a/graphs/directed_and_undirected_weighted_graph.py b/graphs/directed_and_undirected_weighted_graph.py
index 91e83731b..640da1bad 100644
--- a/graphs/directed_and_undirected_weighted_graph.py
+++ b/graphs/directed_and_undirected_weighted_graph.py
@@ -10,23 +10,17 @@ Useful Links: https://www.geeksforgeeks.org/applications-advantages-and-disadvan
               https://en.wikipedia.org/wiki/Graph_(discrete_mathematics)
 """
 
+
 from collections import deque
 from math import floor
 from random import random
 from time import time
 
 class DirectedGraph:
-    def __init__(self) -> None:
-        """
-        Initialize a directed graph.
-
-        >>> g = DirectedGraph()
-        >>> g.all_nodes()
-        []
-        """
+    def __init__(self):
         self.graph = {}
 
-    def add_pair(self, u: int, v: int, w: int = 1) -> None:
+    def add_pair(self, u, v, w=1):
         """
         Add a directed edge from u to v with weight w.
 
@@ -36,14 +30,14 @@ class DirectedGraph:
         {1: [[3, 2]], 2: []}
         """
         if self.graph.get(u):
-            if not any(edge[1] == v and edge[0] == w for edge in self.graph[u]):
+            if self.graph[u].count([w, v]) == 0:
                 self.graph[u].append([w, v])
         else:
             self.graph[u] = [[w, v]]
-        if v not in self.graph:
+        if not self.graph.get(v):
             self.graph[v] = []
 
-    def all_nodes(self) -> list:
+    def all_nodes(self):
         """
         Return a list of all nodes in the graph.
 
@@ -54,7 +48,7 @@ class DirectedGraph:
         """
         return list(self.graph)
 
-    def remove_pair(self, u: int, v: int) -> None:
+    def remove_pair(self, u, v):
         """
         Remove the directed edge from u to v.
 
@@ -65,9 +59,11 @@ class DirectedGraph:
         {1: [], 2: []}
         """
         if self.graph.get(u):
-            self.graph[u] = [edge for edge in self.graph[u] if edge[1] != v]
+            for _ in self.graph[u]:
+                if _[1] == v:
+                    self.graph[u].remove(_)
 
-    def dfs(self, s: int = -2, d: int = -1) -> list:
+    def dfs(self, s=-2, d=-1):
         """
         Perform depth-first search from node s to d.
 
@@ -76,6 +72,8 @@ class DirectedGraph:
         >>> g.add_pair(2, 3)
         >>> g.dfs(1, 3)
         [1, 2, 3]
+        >>> g.dfs(1, 2)
+        [1, 2]
         """
         if s == d:
             return []
@@ -85,23 +83,48 @@ class DirectedGraph:
             s = next(iter(self.graph))
         stack.append(s)
         visited.append(s)
-        while stack:
-            current = stack[-1]
-            if current == d:
-                return visited
-            if current in self.graph:
-                for edge in self.graph[current]:
-                    if edge[1] not in visited:
-                        stack.append(edge[1])
-                        visited.append(edge[1])
-                        break
-                else:
-                    stack.pop()
-            else:
-                stack.pop()
-        return visited
+        while True:
+            if len(self.graph[s]) != 0:
+                ss = s
+                for node in self.graph[s]:
+                    if visited.count(node[1]) < 1:
+                        if node[1] == d:
+                            visited.append(d)
+                            return visited
+                        else:
+                            stack.append(node[1])
+                            visited.append(node[1])
+                            ss = node[1]
+                            break
 
-    def bfs(self, s: int = -2) -> list:
+            if s == ss:
+                stack.pop()
+                if len(stack) != 0:
+                    s = stack[len(stack) - 1]
+            else:
+                s = ss
+
+            if len(stack) == 0:
+                return visited
+
+    def fill_graph_randomly(self, c=-1):
+        """
+        Fill the graph with random edges.
+
+        >>> g = DirectedGraph()
+        >>> g.fill_graph_randomly(5)
+        >>> len(g.all_nodes()) > 0
+        True
+        """
+        if c == -1:
+            c = floor(random() * 10000) + 10
+        for i in range(c):
+            for _ in range(floor(random() * 102) + 1):
+                n = floor(random() * c) + 1
+                if n != i:
+                    self.add_pair(i, n, 1)
+
+    def bfs(self, s=-2):
         """
         Perform breadth-first search starting from node s.
 
@@ -118,15 +141,134 @@ class DirectedGraph:
         d.append(s)
         visited.append(s)
         while d:
-            current = d.popleft()
-            if current in self.graph:
-                for edge in self.graph[current]:
-                    if edge[1] not in visited:
-                        d.append(edge[1])
-                        visited.append(edge[1])
+            s = d.popleft()
+            if len(self.graph[s]) != 0:
+                for node in self.graph[s]:
+                    if visited.count(node[1]) < 1:
+                        d.append(node[1])
+                        visited.append(node[1])
         return visited
 
-    def has_cycle(self) -> bool:
+    def in_degree(self, u):
+        """
+        Calculate in-degree of node u.
+
+        >>> g = DirectedGraph()
+        >>> g.add_pair(1, 2)
+        >>> g.in_degree(2)
+        1
+        """
+        count = 0
+        for x in self.graph:
+            for y in self.graph[x]:
+                if y[1] == u:
+                    count += 1
+        return count
+
+    def out_degree(self, u):
+        """
+        Calculate out-degree of node u.
+
+        >>> g = DirectedGraph()
+        >>> g.add_pair(1, 2)
+        >>> g.out_degree(1)
+        1
+        """
+        return len(self.graph[u])
+
+    def topological_sort(self, s=-2):
+        """
+        Perform topological sort of the graph.
+
+        >>> g = DirectedGraph()
+        >>> g.add_pair(1, 2)
+        >>> g.add_pair(2, 3)
+        >>> g.topological_sort()
+        [1, 2, 3]
+        """
+        stack = []
+        visited = []
+        if s == -2:
+            s = next(iter(self.graph))
+        stack.append(s)
+        visited.append(s)
+        sorted_nodes = []
+
+        while True:
+            if len(self.graph[s]) != 0:
+                ss = s
+                for node in self.graph[s]:
+                    if visited.count(node[1]) < 1:
+                        stack.append(node[1])
+                        visited.append(node[1])
+                        ss = node[1]
+                        break
+
+            if s == ss:
+                sorted_nodes.append(stack.pop())
+                if len(stack) != 0:
+                    s = stack[len(stack) - 1]
+            else:
+                s = ss
+
+            if len(stack) == 0:
+                return sorted_nodes
+
+    def cycle_nodes(self):
+        """
+        Get nodes that are part of a cycle.
+
+        >>> g = DirectedGraph()
+        >>> g.add_pair(1, 2)
+        >>> g.add_pair(2, 1)
+        >>> g.cycle_nodes()
+        [1, 2]
+        """
+        stack = []
+        visited = []
+        s = next(iter(self.graph))
+        stack.append(s)
+        visited.append(s)
+        parent = -2
+        indirect_parents = []
+        ss = s
+        anticipating_nodes = set()
+
+        while True:
+            if len(self.graph[s]) != 0:
+                ss = s
+                for node in self.graph[s]:
+                    if (
+                        visited.count(node[1]) > 0
+                        and node[1] != parent
+                        and indirect_parents.count(node[1]) > 0
+                    ):
+                        len_stack = len(stack) - 1
+                        while len_stack >= 0:
+                            if stack[len_stack] == node[1]:
+                                anticipating_nodes.add(node[1])
+                                break
+                            else:
+                                anticipating_nodes.add(stack[len_stack])
+                                len_stack -= 1
+                    if visited.count(node[1]) < 1:
+                        stack.append(node[1])
+                        visited.append(node[1])
+                        ss = node[1]
+                        break
+
+            if s == ss:
+                stack.pop()
+                if len(stack) != 0:
+                    s = stack[len(stack) - 1]
+            else:
+                parent = s
+                s = ss
+
+            if len(stack) == 0:
+                return list(anticipating_nodes)
+
+    def has_cycle(self):
         """
         Check if the graph has a cycle.
 
@@ -136,73 +278,65 @@ class DirectedGraph:
         >>> g.has_cycle()
         True
         """
-        visited = set()
-        rec_stack = set()
+        stack = []
+        visited = []
+        s = next(iter(self.graph))
+        stack.append(s)
+        visited.append(s)
+        parent = -2
+        indirect_parents = []
+        ss = s
 
-        def cycle_util(v):
-            visited.add(v)
-            rec_stack.add(v)
-            for edge in self.graph.get(v, []):
-                if edge[1] not in visited:
-                    if cycle_util(edge[1]):
+        while True:
+            if len(self.graph[s]) != 0:
+                ss = s
+                for node in self.graph[s]:
+                    if (
+                        visited.count(node[1]) > 0
+                        and node[1] != parent
+                        and indirect_parents.count(node[1]) > 0
+                    ):
                         return True
-                elif edge[1] in rec_stack:
-                    return True
-            rec_stack.remove(v)
-            return False
+                    if visited.count(node[1]) < 1:
+                        stack.append(node[1])
+                        visited.append(node[1])
+                        ss = node[1]
+                        break
 
-        for node in self.graph:
-            if node not in visited:
-                if cycle_util(node):
-                    return True
-        return False
+            if s == ss:
+                stack.pop()
+                if len(stack) != 0:
+                    s = stack[len(stack) - 1]
+            else:
+                s = ss
 
-    # Additional methods would go here with doctests...
+            if len(stack) == 0:
+                return False
 
-class Graph:
-    def __init__(self) -> None:
+    def dfs_time(self, s=-2, e=-1):
         """
-        Initialize an undirected graph.
+        Measure the time taken for DFS.
 
-        >>> g = Graph()
-        >>> g.all_nodes()
-        []
-        """
-        self.graph = {}
-
-    def add_pair(self, u: int, v: int, w: int = 1) -> None:
-        """
-        Add an undirected edge between u and v with weight w.
-
-        >>> g = Graph()
-        >>> g.add_pair(1, 2, 3)
-        >>> g.graph
-        {1: [[3, 2]], 2: [[3, 1]]}
-        """
-        if self.graph.get(u):
-            if not any(edge[1] == v and edge[0] == w for edge in self.graph[u]):
-                self.graph[u].append([w, v])
-        else:
-            self.graph[u] = [[w, v]]
-        if self.graph.get(v):
-            if not any(edge[1] == u and edge[0] == w for edge in self.graph[v]):
-                self.graph[v].append([w, u])
-        else:
-            self.graph[v] = [[w, u]]
-
-    def all_nodes(self) -> list:
-        """
-        Return a list of all nodes in the graph.
-
-        >>> g = Graph()
+        >>> g = DirectedGraph()
         >>> g.add_pair(1, 2)
-        >>> g.all_nodes()
-        [1, 2]
+        >>> g.dfs_time(1, 2) >= 0
+        True
         """
-        return list(self.graph)
+        begin = time()
+        self.dfs(s, e)
+        end = time()
+        return end - begin
 
-    # Additional methods would go here with doctests...
+    def bfs_time(self, s=-2):
+        """
+        Measure the time taken for BFS.
 
-if __name__ == "__main__":
-    import doctest
-    doctest.testmod()
+        >>> g = DirectedGraph()
+        >>> g.add_pair(1, 2)
+        >>> g.bfs_time(1) >= 0
+        True
+        """
+        begin = time()
+        self.bfs(s)
+        end = time()
+        return end - begin