Coding Recipies: Knight's Shortest Path

Coding Recipies: Knight's Shortest Path
          Given a Source and Destination , find the minimum number of moves required to move a knight from Source to Destination.

Fig: Movement of Knight from Source to Destination

X. BFS

public static int path(int[][] board, int startRow, int startCol, int endRow, int endCol) {
  queue = new LinkedList<Coordinate>();
  queue.add(new Coordinate(startRow, startCol));
  queue.add(null);  //this acts a delimiter
  board[startRow][startCol] = 0;
  int hops=0;

  while (!queue.isEmpty()) {
   Coordinate popedItem = queue.poll();

   if (popedItem == null) {
    hops++;
    queue.offer(null);
    //System.out.println("======");
    continue;
   } 
   
    int r = popedItem.row;
    int c = popedItem.col;

    board[r][c] = hops;
    
    //System.out.println(hops + " " + r + " " + c);
    
    if(r==endRow && c==endCol)
    {
     printSol(board);
     return hops;
    }
     

    Coordinate[] points = validCoordinates(board, r, c);

    for (Coordinate o : points) {
     if (o != null)
      queue.add(o);
    }
  }
  return -1;
 }

http://www.java3z.com/cwbwebhome/article/article17/acm140.html
https://www.codechef.com/SNACKTST/problems/KNIGHT1
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