Sudoku Strategies (Easy Level)
Lately, I have been obsessed with Daily Sudoku on Facebook. I especially enjoy playing the easy puzzles because they can be solved without pencil! Only one strategy is necessary to solve easy puzzles quickly and reliably, outlined below.
Warm Up: Cross Hatching
The warm up round consists of filling in the obvious squares through a method known as cross hatching. In sudoku, no number (1 through 9) can repeat in any 3x3 box, row, or column. By process of elimination, we can fill in conscripted cells that meet this criteria.
Ex. Cross Hatching in Action
In this game, we see that the “9” in the center 3x3 box can be solved through cross-hatching. The middle and right columns are blocked by “9”s on the top and bottom. The top row is blocked by the “9” on the right. The middle row is blocked by the “6” already in the box. Thus, the “9” in the middle 3x3 grid only has one option.
Pro-tip:
Scan the entire grid and start with the most populous numbers. If there are already 7/9 “3”s on the board and only 2/9 “5”s, start with the “3”s. This will make it easier to fill in sparser numbers later on through process of elimination with fewer cells available.
The One Strategy to Learn: Advanced Cross Hatching
Advanced cross hatching sounds intimidating but only requires one additional step. Sometimes, a cell is conscripted but it is not immediately evident.
Figure Left: We can immediately determine where the “8” in the bottom right 3x3 box should go. However, by using basic cross hatching, there are 2 possibilities (top center and center center).
Figure Center: We can address this problem by looking at neighboring 3x3 boxes. If we examine the bottom center 3x3 box, we see that the “8” must go in either the center center or center right locations. This creates a new “cross hatch” as now we know the center row is blocked off!
Figure Right: Now we can confidently place the “8” in the top center. With practice, you can quickly spot cases of advanced cross hatching and be able to place numbers without pencil.
With cross hatching and advanced cross hatching, you should be able to solve every single easy level Daily Sudoku game on Facebook. I try to minimize the use of penciling in numbers to maximize my sudoku solving time and score. Plus, avoiding pencil is more fun! Hope this is helpful. Let me know if you have any questions.
P. S. I wrote this article in an airport and a friendly lady saw my computer screen and said, “it’s addicting isn’t it. I’ve spent hours on that game…” before slowly walking away.
