1791. Find Center of Star Graph

Easy

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 <= 10^5

• edges.length == n - 1

• edges[i].length == 2

• 1 <= ui, vi <= n

• ui != vi

• The given edges represent a valid star graph.

解題

func findCenter(edges [][]int) int {
    n := len(edges)
    indegree := make([]int, n + 1)
    for _, edge := range edges {
        indegree[edge[0] - 1]++
        indegree[edge[1] - 1]++

        if indegree[edge[0] - 1] == n {
            return edge[0] 
        }

        if indegree[edge[1] - 1] == n {
            return edge[1] 
        }
    }

    return 0
}