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Platon Sudoku · Sudoku Study

Two-String Kite · Step-by-step example

One strong row link and one strong column link use the same digit. One end from each link lies in a common box. Remove the digit from a cell that sees both remaining ends.

This course is adapted from Platon Sudoku App. Read the complete example here, then continue learning and practising in the app.

View on Google Play

Recognize the pattern

One strong row link and one strong column link use the same digit. One end from each link lies in a common box.

How to find it

Choose a digit and find a row and a column with exactly two candidates each. Look for one end of each inside the same box.

What it allows

Remove the digit from a cell that sees both remaining ends.

Avoid the mix-up

The two box ends must be different cells; the far ends do not need to share a region. The target must see both far ends.

Step-by-step example · Row and column

This example starts from a saved intermediate position. Its candidates include earlier logical eliminations; they are not fresh automatic notes.

Blue: evidence. Green: conclusion. Crossed-out digits: eliminated candidates. R1C1 means row 1, column 1.

Step 1 · Find the row and column strong links

For 9, row 1 has the strong link R1C3–R1C6, and column 4 has the strong link R6C4–R3C4. The inner ends R1C6 and R3C4 share box 2, connecting the two links. The outlined cell is the target.

For 9, row 1 has the strong link R1C3–R1C6, and column 4 has the strong link R6C4–R3C4. The inner ends R1C6 and R3C4 share box 2, connecting the two links. The outlined cell is the target.
For 9, row 1 has the strong link R1C3–R1C6, and column 4 has the strong link R6C4–R3C4. The inner ends R1C6 and R3C4 share box 2, connecting the two links. The outlined cell is the target.
Step 2 · Try an assumption

Assume R6C3 is 9 (? means temporary). R1C3 shares column 3 with R6C3, so it cannot be 9. R6C4 shares row 6 with R6C3, so it cannot be 9.

Assume R6C3 is 9 (? means temporary). R1C3 shares column 3 with R6C3, so it cannot be 9. R6C4 shares row 6 with R6C3, so it cannot be 9.
Assume R6C3 is 9 (? means temporary). R1C3 shares column 3 with R6C3, so it cannot be 9. R6C4 shares row 6 with R6C3, so it cannot be 9.
Step 3 · This creates a conflict

With R1C3 and R6C4 both ruled out, row 1 forces R1C6 to be 9, while column 4 forces R3C4 to be 9. But R1C6 and R3C4 share box 2. A box cannot contain two 9s.

With R1C3 and R6C4 both ruled out, row 1 forces R1C6 to be 9, while column 4 forces R3C4 to be 9. But R1C6 and R3C4 share box 2. A box cannot contain two 9s.
With R1C3 and R6C4 both ruled out, row 1 forces R1C6 to be 9, while column 4 forces R3C4 to be 9. But R1C6 and R3C4 share box 2. A box cannot contain two 9s.
Step 4 · Why we can remove it

The assumption creates two 9s in one box, so it cannot be right. Remove 9 from R6C3.

The assumption creates two 9s in one box, so it cannot be right. Remove 9 from R6C3.
The assumption creates two 9s in one box, so it cannot be right. Remove 9 from R6C3.

What it allows

The assumption creates two 9s in one box, so it cannot be right. Remove 9 from R6C3.

Two-String Kite · Remove the digit from a cell that sees both remaining ends.
Two-String Kite · Remove the digit from a cell that sees both remaining ends.

Practice

This course is adapted from Platon Sudoku App. Read the complete example here, then continue learning and practising in the app.

View on Google Play