LeetCode 310. 最小高度树

Posted 2021-10-12 Blocking The Sky

class Solution {
public:
    vector<int> findMinHeightTrees(int n, vector<vector<int>>& edges) {
        vector<int> minvex;
        if(n==1){
            return {0};
        }
        else if(n==2){
            return {0,1};
        }
        vector<vector<int>> graph(n, vector<int>());
        int degree[n+1];
        memset(degree, 0, sizeof(int) * n);
        for (vector<int>& edge : edges)
        {
            ++degree[edge[0]];
            ++degree[edge[1]];
            graph[edge[0]].push_back(edge[1]);
            graph[edge[1]].push_back(edge[0]);
        }
        queue<int> q;
        int cnt;
        for(int i=0;i<n;i++){
            if(degree[i]==1){
                q.push(i);
            }
        }
        cnt=q.size();
        int m=n;
        while(m>2){
            m-=cnt;
            for(int j=0;j<cnt;j++){
                int temp;
                temp=q.front();
                q.pop();
                degree[temp]=0;
                for(int next : graph[temp]){
                    if(degree[next]!=0){
                        degree[next]--;
                        if(degree[next]==1){
                            q.push(next);
                        }
                    }
                }
            }
            cnt=q.size();
        }
        while(!q.empty()){
            minvex.push_back(q.front());
            q.pop();
        }
        return minvex;
    }
};