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

Nihal Agarwal — Sun, 29 May 2022 22:51:41 +0000

When I am solving questions on Dijkstra's, I had basically two-way (or Java template) to write code for Dijkstra's, but for some questions, problem solved by both ways (or Dijkstra's Java templates) (https://leetcode.com/problems/network-delay-time/) are accepted and for some (e.g., https://leetcode.com/problems/path-with-minimum-effort/), anyone is able to solve the question.

For a graph (represented in Adjacency List):

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

1. Dijkstra's - One way

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 node
dist[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 );
         }
     }
 }

2. Dijkstra's - Second way

 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] } );
         }
     }
 }

Can anyone, help me to know which is the right way (1st or 2nd).

How to draw Triangle star pattern with MySQL without using Stored Procedure?

Nihal Agarwal — Fri, 26 Jun 2020 16:59:00 +0000

Jun 24 '20 Comments: 1 Answers: 2

Triangular pattern example The above pattern is for p(5). How to write a query to print the pattern P(n) (where n is Integer defining the number of rows) using MySQL without using Stored Procedure. I had one code example for MS SQL Server i.e.

DECLARE @i INT = 20

…

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

How to draw Triangle star pattern with MySQL without using Stored Procedure?