Create Find if Path Exists in Graph - Leetcode 1971.py

Author: gahogg

Find if Path Exists in Graph - Leetcode 1971.py

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+# DFS with Recursion
+class Solution:
+    def validPath(self, n: int, edges: List[List[int]], source: int, destination: int) -> bool:
+        if source == destination:
+            return True
+        
+        graph = defaultdict(list)
+        for u, v in edges:
+            graph[u].append(v)
+            graph[v].append(u)
+        
+        seen = set()
+        seen.add(source)
+
+        def dfs(i):
+            if i == destination:
+                return True
+            
+            for nei_node in graph[i]:
+                if nei_node not in seen:
+                    seen.add(nei_node)
+                    if dfs(nei_node):
+                        return True
+            
+            return False
+        
+        return dfs(source) # Time: O(N + E), Space: O(N + E)
+
+# Iterative DFS with Stack
+
+class Solution:
+    def validPath(self, n: int, edges: List[List[int]], source: int, destination: int) -> bool:
+        if source == destination:
+            return True
+        
+        graph = defaultdict(list)
+        for u, v in edges:
+            graph[u].append(v)
+            graph[v].append(u)
+        
+        seen = set()
+        seen.add(source)
+        stack = [source]
+
+        while stack:
+            node = stack.pop()
+            if node == destination:
+                return True
+            for nei_node in graph[node]:
+                if nei_node not in seen:
+                    seen.add(nei_node)
+                    stack.append(nei_node)
+        
+        return False # Time: O(N + E), Space: O(N + E)
+
+
+# BFS with Deque
+
+from collections import deque
+class Solution:
+    def validPath(self, n: int, edges: List[List[int]], source: int, destination: int) -> bool:
+        if source == destination:
+            return True
+        
+        graph = defaultdict(list)
+        for u, v in edges:
+            graph[u].append(v)
+            graph[v].append(u)
+        
+        seen = set()
+        seen.add(source)
+        q = deque()
+        q.append(source)
+
+        while q:
+            node = q.popleft()
+            if node == destination:
+                return True
+            for nei_node in graph[node]:
+                if nei_node not in seen:
+                    seen.add(nei_node)
+                    q.append(nei_node)
+        
+        return False # Time: O(N + E), Space: O(N + E)