Added question 133.

Author: luceCoding

leetcode/medium/133_clone_graph.md

@@ -0,0 +1,32 @@
+# 133. Clone Graph
+
+## Dictionary and DFS Solution
+- Runtime: O(V + E)
+- Space: O(V)
+- V = Vertices
+- E = Edges
+
+We can use a dictionary as a map to the cloned node, then by using DFS, we can figure out the cloned node in relation to the nodes in the graph.
+As we visit each node with DFS, we can create a clone of each neighbor and add them to the current node's cloned node using the dictionary.
+After that, we can call DFS on each neighbor.
+
+```
+class Solution:
+    def cloneGraph(self, node: 'Node') -> 'Node':
+
+        def dfs_clone(curr):
+            if curr in visited:
+                return
+            visited.add(curr)
+            for neighbor in curr.neighbors:
+                if neighbor not in node_to_clone:
+                    node_to_clone[neighbor] = Node(neighbor.val, [])
+                node_to_clone[curr].neighbors.append(node_to_clone[neighbor])
+                dfs_clone(neighbor)
+
+        node_to_clone = dict()
+        node_to_clone[node] = Node(node.val, [])
+        visited = set()
+        dfs_clone(node)
+        return node_to_clone[node]
+```