Today I have done leetcode's June LeetCoding Challenge with cpp.

June LeetCoding Challenge 27

Description

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.

Solution

class Solution {
public:
  int findCenter(vector<vector<int>>& edges) {
    vector<int> degree(edges.size() + 2);
    for(auto &edge : edges) {
      degree[edge[0]] += 1;
      degree[edge[1]] += 1;
      if(degree[edge[0]] > 1) return edge[0];
      if(degree[edge[1]] > 1) return edge[1];
    }
    return -1;
  }
};