Leetcode 743. 网络延迟时间 DisjKstra+Floyd

DisjKstra算法

class Solution {
public:
    int networkDelayTime(vector<vector<int>>& times, int N, int K) {
        //DisjKstra算法
        vector<vector<long long>> dis(N+1, vector<long long>(N+1, INT_MAX));
        vector<int> vis(N+1, 0);
        int ans = 0;        

        for(int i=0; i<=N;i++)
            dis[i][i] = 0;

        for(int i=0; i<times.size(); i++)
            dis[times[i][0]][times[i][1]] = times[i][2];
        
        vis[K] = 1;

        for(int i=1; i<N; i++){
            int node = 0, minn = INT_MAX;

            for(int j=1; j<=N; j++){
                if(!vis[j] && dis[K][j] <= minn){
                    minn = dis[K][j];
                    node = j;
                }
            }

            vis[node] = 1;

            for(int j=1; j<=N; j++)          
                dis[K][j] = min(dis[K][j], dis[K][node] + dis[node][j]);
        } 

        for(int i=1; i<=N; i++){
            if(dis[K][i] == INT_MAX)
                return -1;
            ans = max(ans, (int)dis[K][i]);
        }           

        return ans;   
    }
};

Floyd算法

class Solution {
public:
    int networkDelayTime(vector<vector<int>>& times, int N, int K) {
        //Floyd算法
        vector<vector<long long>> dis(N+1, vector<long long>(N+1, INT_MAX));
        int ans = 0;

        for(int i=0; i<=N;i++)
            dis[i][i] = 0;
        
        for(int i=0; i<times.size(); i++)
            dis[times[i][0]][times[i][1]] = times[i][2];

        for(int k=1; k<=N; k++)
            for(int i=1; i<=N; i++)
                for(int j=1; j<=N; j++)
                    dis[i][j] = min(dis[i][j], dis[i][k] + dis[k][j]);

        for(int i=1; i<=N; i++){
            if(dis[K][i] == INT_MAX)
                return -1;
            ans = max(ans, (int)dis[K][i]);
        }

        return ans;
    }
};