Sudoku Solver

Expert

2-String Kite

Two strong links (one row, one column) connected in a box, eliminating candidates from the intersection.

The 2-String Kite is a powerful single-digit strategy that, like the Skyscraper, is a variation of the Turbot Fish.

While the Skyscraper connects two parallel lines (Row-Row or Col-Col), the 2-String Kite connects a Row and a Column.

Interactive Example

1 2 3 4 5 6 7 8 9
9
1 2 3 4 5 6 7 8 9
2
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
8
1 2 3 4 5 6 7 8 9
4
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
5
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
8
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
1
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
6
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
4
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
7
1 2 3 4 5 6 7 8 9
8
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
2
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
1
1 2 3 4 5 6 7 8 9
3
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
6
1 2 3 4 5 6 7 8 9
1
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
4
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
3
1 2 3 4 5 6 7 8 9
5
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
9
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
3
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
9
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
4
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
1
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
9
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
8
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9
6
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8 9

Click "Apply Logic" to see the strategy in action.

Real Example Explanation

In the interactive example above, look at the number 4:

  1. String 1 (The Row): Look at Row 4.
    • The 4 appears only twice: at R4C1 and R4C2.
    • This is a Strong Link: One of them must be a 4.
  2. String 2 (The Column): Look at Column 3.
    • The 4 appears only twice: at R2C3 and R5C3.
    • This is also a Strong Link.
  3. The Knot (The Connection):
    • We need to tie these two strings together.
    • Notice that R4C1 (from the Row) and R5C3 (from the Column) are both in Box 4 (the middle-left 3x3 box).
    • Because they share a box, they "see" each other. They cannot both be 4.
  4. The Logic:
    • If R4C2 is NOT 4 -> Then R4C1 MUST be 4.
    • If R4C1 is 4 -> Then R5C3 cannot be 4 (same box).
    • If R5C3 is NOT 4 -> Then R2C3 MUST be 4.
    • Result: Either the start of the chain (R4C2) is 4, or the end of the chain (R2C3) is 4.
  5. The Elimination:
    • Since at least one of the endpoints (R4C2 or R2C3) must be a 4, any cell that sees BOTH can be cleared.
    • R2C2 sees R4C2 (Column 2) and R2C3 (Row 2). It cannot be a 4.

How to Spot It

  1. Pick a Number: Scan rows and columns for Strong Links (where the number appears exactly twice).
  2. Find a Corner: Look for a Row-Link and a Col-Link that meet in a common 3x3 Box.
  3. Check the "Knot": The ends meeting in the box must be different cells.
  4. Identify Endpoints: The other ends of the strings (outside the box) are your "Kite Tips".
  5. Eliminate: Remove the candidate from any cell seeing both Tips.

Quick Comparison

  • Skyscraper: 2 Rows (or 2 Cols) connected by a column/row. Parallel lines.
  • 2-String Kite: 1 Row and 1 Col connected by a Box. Perpendicular lines.