As I've continued to grow in my ability to solve Sudoku puzzles, I've also continued to seek out more advanced puzzles to push and challenge myself to learn and understand techniques that are necessary in order to complete "Hard+" puzzles.
Keys to finding and using a skyscraper:
1. Look for two columns or two rows where only two possible candidate exist for a number (ie: Columns 1 and 8 have two cells each where a 3 is possible)
2. Identify if each of the four cells you've spotted is in its own box (ie: as you look at each of the four individual cells, the other three do not exist in the same box)
3. Verify that the four cells form a shape where you can see a "base" (two cells are directly in line with each other; in the same row or same column), and the other two cells up or across from it do not line up directly (these two staggered cells for the "roof tops"). To double check yourself, look at where you think you've spotted a "base" and then look up or across to where the other two cells are. If the other two cells also line up, then you have incorrectly spotted the base. Pick another set of cells that are directly in line with each other and do the same test to verify if the cells across from it are directly in line with each other, or if they are staggered. Once you verify that you can see a base and a staggered top, you've correctly identified the correct aspects of the skyscraper.
4. Now focus on the roof tops. Start at the lowest part of the roof top - from that cell, looking across the row or column towards the highest part of the roof top, look for cells where other possible candidates exist that are visible by both roof tops. Any cells you find can be elimated as possibilities. Do the same thing with the upper roof top now - Look across the row or column towards the lower roof top and find cells where other possible candidates exist that are visible by both roof tops. These can also be eliminated.
NOTE: Whether you look across rows or coumns when dealing with the roof tops will depend on how the skyscraper is positioned on the board. This is why I state in step 4 to look across the row or column where the roof tops are because it will depend on how the skyscraper is oriented. If the base runs parallel to the bottom of your puzzle grid, then the roof tops will sight each other across rows. If the skyscraper is oriented 90 degrees clockwise or counter-clockwise, then the base will be running parallel to the left or right side of your puzzle grid, which means that your roof tops will sight each other across columns.
If anyone watching this video would like to see other examples of this particular technique, let me know and I'll post one or more videos demonstrating it. Or, if you think I did a crappy job and you'd like me to do better, let me know what I can do to improve :).
If you'd like to keep growing in your Sudoku skills, but you're not quite ready for this level, keep practicing beginner to intermediate puzzles until you feel more comfortable and confident to take on new challenges like this and other techniques I'll be demonstrating in the months to come.
I'd like to give a shout out to Tiffany ( / misskity6 . She has some great videos on her channel where she demonstrates beginner to intermediate techniques that are crucial to building a solid foundation.
I'd also like to give a shout out to Angus Johnson for making the game "Simple Sudoku", which is the game I was using to demonstrate the skyscraper technique. Check out his site:
www.angusj.com/sudoku/
27 дек 2013
