Problem's faced in Dijkstra's Java Code || Leetcode

ArrayList<int[]>[] graph = new ArrayList[n]; // n represents number of nodes.

boolean[] vis = new boolean[n];int[] dist = new int[n];Arrays.fill( dist, Integer.MAX_VALUE );PriorityQueue<Integer> q = new PriorityQueue<>( (a,b) -> dist[a] - dist[b] );q.add( 0 ); // Starting nodedist[start] = 0; while( !q.isEmpty() ) {     int node = q.poll();     if( vis[node] )         continue;     vis[node] = true;     // traversing neighboours     for( int[] nb : graph[node] )     {         int node2 = nb[0];         int weight = nb[1];         if( !vis[node2] && dist[node2] > dist[node] + weight )         {             dist[node2] = dist[node] + weight;             q.add( node2 );         }     } }

 boolean[] vis = new boolean[n]; int[] dist = new int[n]; Arrays.fill( dist, Integer.MAX_VALUE ); PriorityQueue<int[]> q = new PriorityQueue<>( (a,b) -> a[1] - b[1] ); q.add( new int[2] ); // Starting node dist[start] = 0; while( !q.isEmpty() ) {     int node = q.peek()[0];     int dis = q.peek()[1];     if( vis[node] )         continue;     vis[node] = true;     // traversing neighboours     for( int[] nb : graph[node] )     {         int node2 = nb[0];         int weight = nb[1];         if( !vis[node2] && dist[node2] > dis + weight )         {             dist[node2] = dis + weight;             q.add( new int[] { node2, dist[node2] } );         }     } }