Solving methods > 2 Locked candidates
The preceding methods permitted to directly assign a value to a cell.
The following permit to reduce the possible candidates for a cell in order to finally find a single value for the cell.
2.1 Segment 1
When in a block, if a number is only possible in one segment, then the candidate can be excluded from that row or column in the other blocks.

In the 3rd block (upper right), 6 is only possible in the top segment (G1&H1). 6 has to be on the first row of this block. 6 can be eliminated from C1.
For the 3rd block, 6 is not possible in the 2nd row since it is already in E2. It is not possible in the 3rd row as there are already two numbers assigned (4&3) and 6 is already in row I, in I4.



2.2 Segment 2
When in a row or column only one block can contain a number, that number can be excluded for the other cells in that block.

On the 3rd row, only the 2nd block can contain 2 (in D3&E3) Therefore 2 cannot be assigned on the 1st and 2nd rows in this block.
Given the numbers already assigned on the 3rd row, and the two wich are assigned in columns B&H, 2 must be on the 3rd row in the 2nd block. 2 can thus be eliminated from D1,E1,E2 and F2.




