This is the first puzzle of this type which I created for practice of Indian Puzzle Team participating in World Puzzle Championship 2009. I have created some more puzzles of this type, which I will be posting here later.
This Puzzle type appeared in the following championships
"18th World Puzzle Championship, Antalya (Turkey)"
Fill in every circle inside and outside the grid with one of the given prime numbers. Prime numbers larger than those given are not needed. Locations of all prime numbers inside and outside the grid are given as circles.
Draw a snake of numbers in the diagram that starts with 1, grows in value with every visited adjacent square and ends at a prime number. The snake goes through all circles inside the grid and does not touch itself, not even diagonally. The numbers outside the grid indicate the number of squares that are occupied by the snake in the corresponding direction.