Here's what you can do Vikas Poonia, i have shared you the Algo for your question!

1) Initialize the largest three elements as minus infinite.

first = second = third = -∞

2) Iterate through all elements of array.

 a) Let current array element be x.

   b) If (x > first)
      {
          // This order of assignment is important
          third = second
          second = first
          first = x   
       }

   c)  Else if (x > second)
      {
          third = second
          second = x 
      }

   d)  Else if (x > third)
      {
          third = x  
      }

3) Print first, second and third.

Please Let me know if you have any queries, will be happy to help 😇