261. Graph Valid Tree

You have a graph of n nodes labeled from 0 to n - 1. You are given an integer n and a list of edges where edges[i] = [ai, bi] indicates that there is an undirected edge between nodes ai and bi in the graph.

Return true if the edges of the given graph make up a valid tree, and false otherwise.

 def validTree1(n: int, edges: List[List[int]]):

   
        visited = set()
        def hasCycle(node, cameFrom):
           
            if node in visited:
                return True                
            visited.add(node)
                   
            for nei in edgeMap[node]:
                if nei != cameFrom:                    
                    detected = hasCycle(nei, node)
                    if detected:
                        return True
                   
            return False
       
        edgeMap = {}
        for i in range(n):
            edgeMap[i] = []
        for e in edges:
            edgeMap[e[0]].append(e[1])
            edgeMap[e[1]].append(e[0])
       
        return not hasCycle(0, -1) and len(visited) == n



   
def validTree(n: int, edges: List[List[int]]):

    if len(edges) != n - 1:
        return False
           
    visited = set()
   
    def dfs(node):
        if node in visited:
            return
        visited.add(node)
       
        for neighbour in edgeMap[node]:
            dfs(neighbour)

    edgeMap = {}
    for i in range(n):
        edgeMap[i] = []
    for e in edges:
        edgeMap[e[0]].append(e[1])
        edgeMap[e[1]].append(e[0])
       
    dfs(0)
    return len(visited) == n

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