There is an undirected star graph consisting of n
nodes labeled from 1
to n
. A star graph is a graph where there is one center node and exactly n - 1
edges that connect the center node with every other node.
You are given a 2D integer array edges
where each edges[i] = [ui, vi]
indicates that there is an edge between the nodes ui
and vi
. Return the center of the given star graph.
Example 1:
Input: edges = [[1,2],[2,3],[4,2]]
Output: 2
Explanation: As shown in the figure above, node 2 is connected to every other node, so 2 is the center.
Example 2:
Input: edges = [[1,2],[5,1],[1,3],[1,4]]
Output: 1
Constraints:
-
3 <= n <= 105
-
edges.length == n - 1
-
edges[i].length == 2
-
1 <= ui, vi <= n
-
ui != vi
- The given
edges
represent a valid star graph.
SOLUTION:
class Solution:
def findCenter(self, edges: List[List[int]]) -> int:
graph = {}
for a, b in edges:
if a in graph:
graph[a][0] += 1
graph[a][1] += 1
else:
graph[a] = [1, 1]
if b in graph:
graph[b][1] += 1
graph[a][0] += 1
else:
graph[b] = [1, 1]
k = len(graph) - 1
for node in graph:
if graph[node][1] == k:
return node
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