[LeetCode] 1791. Find Center of Star Graph

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.

class Solution:
    def findCenter(self, edges: List[List[int]]) -> int:
        
        import itertools
        new_edges = list(itertools.chain.from_iterable(edges))

        s1 = list(set(new_edges)) # set 으로 unique value 
        s2 = [0 for i in range(len(s1))] # count +=1 하기 위해서 리스트 생성 

        dict1 = dict(zip(s1,s2)) # dict 형태로 리스트 요소들 변환 

        for k in new_edges: 
            if k in dict1:
                dict1[k] +=1

        key_max = max(dict1.keys(), key=(lambda k:dict1[k]))  # key, value 에서 value counting 

        
        return key_max

#Runtime: 764 ms, faster than 96.66% of Python3 online submissions for Find Center of Star Graph.
#Memory Usage: 50.4 MB, less than 21.36% of Python3 online submissions for Find Center of Star Graph.

class Solution:
    def findCenter(self, edges: List[List[int]]) -> int:
        f=edges[0][0] 
        s=edges[0][1]
        if(f in edges[1]):
            return f
        else:
            return s
            
 # 문제의 특징을 잘 잡고 간결하게 풀어냈음.. bb