The locked candidate technique type 2

Hello and welcome to this course on type 2 locked candidates technique!

As we saw in the previous lesson, the locked Candidates technique is a technique of elimination to logically determine which numbers can be eliminated.

The type 2 technique follows the same logic as type 1, but this time focuses more precisely on the cells and not the rows and columns.

Type 2 locked candidates (Claim)

This technique is the complement of the locked candidate technique of type 1.

Let's look at row R3. We have put notes in all the companion cells and we are looking for a candidate in the number 3.

Since we can clearly see that the only possible candidates for the number 3 are the cells R3-C1 and R3-C3, then it is impossible for the cell R1-C3 to contain a 3. So we can delete the candidate with peace of mind.

Second example

Here is another example of type 2 locked candidates.

Let's look at column C1. This time we are looking for candidates with the number 1.

As can be seen in column C1, the only two candidates for the number 1 are in the same cell. Therefore, in this case, the other cells in box 7 cannot contain the digit 1.