Cross Sudoku is a variant of the classic Sudoku puzzle that involves more complexity and challenge due to its structure. It consists of five standard 9x9 Sudoku grids arranged in such a way that they intersect at one common grid, forming a giant cross-like structure. The central grid is shared among all the other four, which are placed on each side (top, bottom, left, and right) of it.
- Grid Structure: The puzzle consists of five 9x9 grids, with one grid at the center and the other four surrounding it, forming a cross.
- Number Placement: Each grid must be filled with numbers from 1 to 9.
- No Repetition: A number cannot be repeated in any row, column, or designated 3x3 square within each 9x9 grid.
- Intersecting Grids: The central grid is common to all the other grids and must obey the rules of all connected grids simultaneously.
- Independence: Although the grids are connected, the left, right, top, and bottom grids operate independently of each other, except for the shared central grid.
Basic Solving Tips
- Start with the Central Grid: Since the central grid is common to all others, solving it first can provide numerous clues for the surrounding grids.
- Single Possibility: Look for squares where only one number can possibly go, considering the rules of Sudoku.
- Elimination: Exclude impossible numbers in a particular square by observing its row, column, and 3x3 square.
- Look for Grid Independence: Solve for rows, columns, and squares in the outer grids that do not intersect with the central grid, as they can be solved like a standard Sudoku.
- Use Pencil Marks: Make small pencil marks of possible numbers in a square and update them as you solve the puzzle to keep track of options.