1791.FindCenterofStarGraph.py

'''
    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:
    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:
    Input: edges = [[1,2],[5,1],[1,3],[1,4]]
    Output: 1

    Constraints:
        - 3 <= n <= 10^5
        - edges.length == n - 1
        - edges[i].length == 2
        - 1 <= ui, vi <= n
        - ui != vi
        - The given edges represent a valid star graph.
'''
#Difficulty: Medium
#60 / 60 test cases passed.
#Runtime: 836 ms
#Memory Usage: 50.7 MB

#Runtime: 836 ms, faster than 56.70% of Python3 online submissions for Find Center of Star Graph.
#Memory Usage: 50.7 MB, less than 16.71% of Python3 online submissions for Find Center of Star Graph.

class Solution:
    def findCenter(self, edges: List[List[int]]) -> int:
        count = {}
        for edge in edges:
            for val in edge:
                if val not in count:
                    count[val] = 0
                count[val] += 1
        return max(count, key=count.get)