1466: Reorder Routes

Reorder Routes to Make All Paths Lead to the City Zero

Author: sumanth-botlagunta

python/reorder_routes_to_make_all_paths_lead_to_city_zero.py

@@ -0,0 +1,26 @@
+# https://leetcode.com/problems/reorder-routes-to-make-all-paths-lead-to-the-city-zero/description/
+# T: O(N) where N is the number of nodes in the graph
+# S: O(N) where N is the number of nodes in the graph
+
+class Solution:
+    def __init__(self):
+        self.reorders = 0
+
+    def minReorder(self, n, connections):
+        edges = {(u, v) for u, v in connections}
+        graph = {i:[] for i in range(n)}
+        for u, v in connections:
+            graph[u].append(v)
+            graph[v].append(u)
+        visit = set()
+        visit.add(0)
+        def dfs(graph, edges, visit, city):
+            for node in graph[city]:
+                if node in visit:
+                    continue
+                if (node, city) not in edges:
+                    self.reorders+=1
+                visit.add(node)
+                dfs(graph, edges, visit, node)
+        dfs(graph, edges, visit, 0)
+        return self.reorders