743. 网络延迟时间-迪杰斯特拉

743. 网络延迟时间-迪杰斯特拉

class Solution {
public:
    int networkDelayTime(vector<vector<int>>& times, int n, int k) {
        const int inf = INT_MAX /2;
        vector<vector<pair<int,int>>> g(n);

        for(auto &t : times){
            int x = t[0] -1 , y = t[1] -1;
            g[x].emplace_back(y,t[2]);
        }
        vector<int> dist(n, inf);
        dist[k-1] =0;
        priority_queue<pair<int,int>,vector<pair<int,int>>,greater<>>  q;
        q.emplace(0,k-1);

        while(!q.empty()){
            auto p = q.top();
            q.pop();

            int time = p.first, x = p.second;
            if(dist[x] < time)
                continue;
            for(auto &e : g[x]){
                int y = e.first, d = e.second + dist[x];
                if(d < dist[y]){
                    dist[y] = d;
                    q.emplace(d,y);
                }

            }
        }
        int ans = *max_element(dist.begin(), dist.end());
        return ans == inf ? -1 :ans;
    }
};