(Author’s note: You need to read the Introductory first to fully understand the terms for the parts of the SUDOKU puzzle, and the Sample Puzzle that I reference in this preview These are included in my complete book.)

Technique 1 starts with a scan of the first horizontal section group(i.e., S1, 2 and 3) and with the digit 1, which will be increased by 1 until it reaches 9. Then you will drop down to the second horizontal group (i.e., S4, 5, and 6) and repeat this technique with digits 1 through 9,with each repetition. Then you will drop down once more to the third (bottom) horizontal section group 3 (i.e., S7, 8, and 9). Each scan will start with digit 1 and be increased by one until it reaches digit 9.

The basic procedure for technique 1 is to scan the horizontal section group and look for two occurrences (a pair) of the same digit number as the iteration (1 through 9) in any two of the three sections and any two of the three rows. (In other words, the first time through this technique, you will be looking for two occurrences of the digit 1; the second time, you will look for two occurrences of the digit 2, and so on). Be sure to scan all three sections and all three rows in the horizontal section group for the number. Note—there will always be one iteration (and probably more) in this technique when you will not find two occurrences of the digit for which you are scanning. You might not even find a

single occurrence of a specific digit. Do not worry. Simply increase your digit by 1 and repeat the scan.

When you find a digit with only two occurrences in the horizontal section group, focus on the one section and the one row that does not have that digit. In that section and row, at least one cell must be empty, and all three cells might be empty.

If there is only one empty cell, it is easy; enter the digit in that cell. Then add 1 to your digit and repeat the scan.

When there are two empty cells in the row, you will have to scan the intersecting columns for each of the empty cells for an occurrence of the digit matching the iteration number in the entire column spanning all nine rows. If either column does not have an occurrence of the digit and the other column does have an occurrence of the digit, it is the column without the occurrence of the digit in which you can correctly enter the digit in the empty cell at the original cell location (section, row, and column). To say this instruction another way, if the digit is found in either column that you scanned, you cannot use that column that contains your digit. If your digit is not found in either column, you cannot decide into which empty cell in the row to enter your digit at the originating

location; it must be left unsolved for this iteration.

When you have completed all of the above with digit 1, add 1 to your digit and repeat this entire technique until you have examined all three horizontal section groups with all the digits, 1 through 9.

Do the following working exercises for this technique before going on to technique 2.

Working Exercise 1

Study the sample puzzle. Focus on the first horizontal section group, and start with the digit 1. Immediately, you see that a 1 appears in sections 1 and 2, in rows 3 and 2. That leaves cells S3R1C7 and 8 available for the digit 1. Scanning the intersecting

columns 7 and 8 for a digit 1, you find the digit in S9R9C8, but you do not find the digit 1 in any cell in column 7. Therefore, enter a 1 in S3R1C7.

Increase your digit to 2, and you find a 2 in S2 and 3, R1 and 3, leaving S1R2C1 and 2 available for the digit 2. Scan the intersecting columns 1 and 2 for the digit 2. You do not find the digit 2 in any cell in column 1, but it is found in S7R8C2. Therefore, enter digit 2 in S1R2C1 (i.e. the column without the digit).

Increase your digit to 3, and you find only one 3 in S3R1C9. You cannot work it because you are looking for pairs of the digit, so increase your digit to 4. There are no 4s in this first horizontal section group, so increase your digit to 5. A 5 occurs in S1 and 3, R1 and 3, leaving S2R2C4 and 5 for the digit. Scan C4 and 5 for a 5. You do not find a 5 in C4, but you do find a 5 in S5R4C5. Enter the 5 in S2R2C4.

Increase your digit to 6. There is only one digit 6 in this horizontal section group, so increase the digit to 7. A 7 occurs in S1 and 2 and R2 and 3, so we have to look at S3R1, where only C8 is empty. (Scanning C8 finds no other 7 in the column; this is just a double check on our accuracy so far. It is a good practice to double-check your work frequently). Enter the 7 in S3R1C8.

Increase your digit to 8, and there is no occurrence of the digit in this section. Increase to 9 and there is only one occurrence. So we are done with the first horizontal section group.