leetcode-com-explore-challenge-card-june-leetcoding-challenge-540-week-2-june-8th-june-14th-3360.cpp

class Solution {
public:
    int findCheapestPrice(int n, vector<vector<int>>& flights, int s, int d, int K) {
         unordered_map<int, vector<pair<int,int>>> g;
       for (const auto& e : flights)
            g[e[0]].emplace_back(e[1], e[2]);        
        int ans = INT_MAX;
        queue<pair<int,int>> q;
        q.push({s,0}); 
        int steps =0; 
        while(!q.empty()){
            int n = q.size();
            for(int i=0; i<n; ++i){
             auto curr=q.front();q.pop();
            if(curr.first == d) ans = min(ans, curr.second);   
            for(auto x:  g[curr.first]){             
               if( curr.second + x.second > ans) continue;
                q.push({x.first,curr.second + x.second });
             }  
            }
          if(steps++ > K) break;
        }
        
        return ans == INT_MAX ? - 1 : ans;
    }
};