Variants

Greater Than Sudoku: Rules & How to Solve

In Greater Than Sudoku the clues are not numbers but comparisons. A < or > sign sits between neighbouring cells, and from those signs alone — plus the usual Sudoku rules — the whole grid is forced. Here is how to read the signs and where to start.

The rules in one minute

The board is an ordinary 9×9. Every row, every column and every 3×3 box must contain the numbers 1 to 9 exactly once, exactly as in classic Sudoku. What changes is where the clues come from. Instead of a scattering of given digits, a sign sits between most pairs of side-by-side cells, and the open side of the sign always points at the larger number. So a sign read as 5 > 2 means the left cell is bigger; 3 < 7 means the right one is. Easier boards hand you a few given numbers to start; harder ones give almost none and lean entirely on the signs.

Find the extremes first

The fastest way in is to hunt for cells that every neighbouring sign points away from, or towards. A cell that is greater than all of its marked neighbours can only be a high number, and if it beats enough of them it must be a 9. The mirror image finds your 1s: a cell smaller than all its neighbours is the strongest candidate for the lowest digit. These extreme cells are the footholds that start the chain of deductions, so scan for them before anything else.

Read the sign chains

Signs rarely sit alone. Inside a box you will often find a run like 2 < 5 > 4, which tells you the middle cell is the largest of the three and both ends are smaller. Longer chains order several cells at once: a < b < c forces a to be at least two below c. You do not always learn the exact numbers from a chain, but you learn their order — and order, combined with the no-repeat rule, is usually enough to squeeze each cell down to a single value.

Then switch to ordinary Sudoku

Once a few numbers are placed, the signs have done their opening work and classic technique takes over. Every digit you fix removes that candidate from its row, column and box, exactly as in a normal game, and those eliminations feed back into the sign chains. The solve becomes a conversation between the two kinds of clue: the comparisons narrow a cell, the placement clears a unit, and the cleared unit sharpens the next comparison.

A short worked example

Suppose three cells in a box read a < b > c, and a fourth sign tells you c > d. Straight away b is the largest of the group and d is the smallest. If the box already contains a 9 elsewhere, b cannot be 9, which caps the whole chain and often pins d to 1 or 2. None of this needed a single given digit — the ordering alone, combined with the numbers the box, row and column have already used, keeps narrowing the options until one survives.

Common mistakes to avoid

The usual slip is reading a sign the wrong way, so fix the rule firmly: the wide, open end faces the bigger number, every time. The second is solving the inequalities and forgetting the ordinary rules — a value can satisfy every nearby sign and still be illegal because it repeats in its row or box. Check both constraints before you commit. And when a board gives you no numbers at all, resist the urge to guess; there is always an extreme cell or a sign chain that forces the next move.

Ready to try it? Play Greater Than Sudoku now. If you enjoy an extra rule layered on the classic grid, Killer Sudoku is a natural next step, and the pure original is always a tap away at Sudoku AZ.