## Difficult Sudoku-7 Group Puzzle

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Place each element of the group (1 2 3 4 5 6 7) exactly once in each row, each column, and each septomino.

### Deductive steps to solve the puzzle

The moves within each step may be done in any order.

All of the moves within a particular step must be done before all of the moves in the subsequent step can be guaranteed to be completed.

Rows are numbered top to bottom, columns from left to right, and rectangles from left to right and then top to bottom. Coordinates are (col, row). Precise details on numbering within each group are specified in the on-line instructions .

Step 1. There are 2 independent moves.

• The only spot left for 3 in the 1st septomino is at (2, 2).
• The only spot left for 2 in the 4th septomino is at (5, 3).

Step 2. There is 1 independent move.

• The only spot left for 5 in the 2nd column is at (2, 7).

Step 3. There is 1 independent move.

• The only spot left for 5 in the 5th row is at (7, 5).

Step 4. There are 3 independent moves.

• The only spot left for 5 in the 4th row is at (1, 4).
• The only spot left for 3 in the 5th row is at (6, 5).
• The only spot left for 5 in the 2nd septomino is at (4, 1).

Step 5. There are 4 independent moves.

• The only spot left for 7 in the 5th row is at (1, 5).
• The only spot left for 3 in the 6th row is at (7, 6).
• The only spot left for 5 in the 3rd septomino is at (3, 2).
• The only spot left for 7 in the 6th septomino is at (4, 6).

Step 6. There are 5 independent moves.

• The only spot left for 7 in the 2nd row is at (6, 2).
• The only spot left for 1 in the 5th row is at (2, 5).
• The only spot left for 7 in the 3rd septomino is at (3, 3).
• The only spot left for 1 in the 5th septomino is at (4, 7).
• The only spot left for 4 in the 6th septomino is at (6, 4).

Step 7. There are 7 independent moves.

• The only spot left for 3 in the 3rd column is at (3, 4).
• The only spot left for 1 in the 6th column is at (6, 1).
• The only spot left for 3 in the 3rd septomino is at (4, 3).
• The only spot left for 1 in the 3rd septomino is at (5, 2).
• The only spot left for 6 in the 6th septomino is at (5, 5).
• The only spot left for 7 in the 7th septomino is at (7, 7).
• The only spot left for 1 in the 7th septomino is at (7, 4).

Step 8. There are 4 independent moves.

• The only spot left for 4 in the 4th column is at (4, 2).
• The only spot left for 1 in the 1st septomino is at (1, 3).
• The only spot left for 6 in the 4th septomino is at (4, 4).
• The only spot left for 4 in the 7th septomino is at (5, 7).

Step 9. There are 5 independent moves.

• The only spot left for 6 in the 2nd row is at (1, 2).
• The only spot left for 4 in the 3rd row is at (7, 3).
• The only spot left for 4 in the 2nd column is at (2, 6).
• The only spot left for 4 in the 1st septomino is at (1, 1).
• The only spot left for 6 in the 3rd septomino is at (2, 3).

Step 10. There are 5 independent moves.

• The only spot left for 6 in the 6th row is at (6, 6).
• The only spot left for 2 in the 1st column is at (1, 6).
• The only spot left for 2 in the 1st septomino is at (3, 1).
• The only spot left for 6 in the 2nd septomino is at (7, 1).
• The only spot left for 6 in the 5th septomino is at (3, 7).

Step 11. There is 1 independent move.

• The only spot left for 2 in the 7th septomino is at (6, 7).