1791. Find Center of Star Graph

Description

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.

 

Solutions

Solution: Greedy

• Time complexity: O(1)
• Space complexity: O(1)

 

JavaScript

/**
 * @param {number[][]} edges
 * @return {number}
 */
const findCenter = function (edges) {
  const [[a, b], [c, d]] = edges;

  if (a === c || a === d) return a;
  return b;
};