C++ Solution 1: Adjacency List

Used Adjacency List to recreate the graph. Then, found which vertex has the max neigbor.

1class Solution {
2  public:
3    int findCenter(vector<vector<int>>& edges) {
4      const int V = edges.size() + 1;
5      vector<int> g[V];
6
7      for(int i=0; i<V-i; ++i) {
8        int u = edges[i][0];
9        int v = edges[i][1];
10
11        g[u-1].push_back(v-1);
12        g[v-1].push_back(u-1);
13      }
14
15      int mx = -1;
16      int mxV = -1;
17
18      for(int i=0; i<V; ++i) {
19        int temp = g[i].size();
20        if(temp > mx) {
21          mx = temp;
22          mxV = i+1;
23        }
24      }
25
26      return mxV;
27    }
28};

C++ Solution 2: Star graph

The fact that the given graph is a star graph, we only need to check first 2 edges and whichever vertex shows up twice, has to be the center.

1class Solution {
2  public:
3    int findCenter(vector<vector<int>>& edges) {
4      int v[] = {edges[0][0], edges[0][1], edges[1][0], edges[1][1]};
5      return (v[0]==v[2] || v[0]==v[3]) ? v[0] : v[1];
6    }
7};