Solution to Sudoku no 602

Sudoku no 602 (Tough)

Solve online

Sudoku grader and solver 

See answer 

Solution to Sudoku no 601

Sudoku no 601 (Easy)

Solve online

Sudoku grader and solver

See answer

Solution to Sudoku no 600

Sudoku no 600 (Extreme)

This is the most difficult sudoku I have created so far, with a Hodoku grade of 14244:

Solve online 

Sudoku grader and solver 

See answer

World's Hardest Sudoku (3)

 Even this site had to guess, which is something I have never seen before (click on the image to see it full size if necessary):

World's Hardest Sudoku (2)

Andrew Stuart's grader and solver got as far as calculating the candidates before giving up:

See if you can carry on from here.

Solution to World's Hardest Sudoku

World's Hardest Sudoku (1)

Arto Inkala created the sudoku puzzle below in 2012 and claimed that it was the most difficult one ever created. I don't usually publish other people's work but I am making an exception in this case as I want to compare this puzzle with one of my own:

Solve online 

Sudoku grader and solver

See answer 

I have given you the usual link to solve the puzzle yourself. I have also given you a link to run it through Andrew Stuart's grader and solver but it failed to find the solution. Finally I ran the puzzle through Hodoku, which gave up and resorted to brute force when the score got to 21342:

800000000003600000070090200050007000000045700000100030001000068008500010090000400 #1 Extreme (21342) bf

Solution to Sudoku no 599

Sudoku no 599 (Tough)

Solve online  

Sudoku grader and solver

See answer

Solution to Sudoku no 598

Sudoku no 598 (Tough)

Solve online

Sudoku grader and solver

See answer 

Solution to Sudoku no 597

Sudoku no 597 (Extreme)

Solve online

Sudoku grader and solver 

See answer 

Solution to Sudoku no 596

Sudoku no 596 (Diabolical)

Solve online

Sudoku grader and solver 

See answer