Sudoku Chain Notation: How to Read r1c1, Links, and Shorthand
Sudoku chain notation is the compact shorthand that hard-puzzle strategy is written in, and it looks like gibberish until the day it suddenly reads like plain English. Terms like r1c1, strong links, and weak links let solvers describe any cell and any logical connection without a paragraph of clumsy prose. Once you can read it, the entire library of advanced tutorials, forum posts, and solver explanations opens up to you. This guide decodes the whole system, one small piece at a time.
Why sudoku chain notation exists
Sudoku chain notation is a compact language for describing where things sit on the grid and how they connect. Once puzzles get hard enough to need chains, X-Wings, and coloring, plain English becomes hopeless: a phrase like the seven in the top-left that links to the seven three squares to the right is slow, wordy, and easy to misread. Sudoku chain notation replaces all of that with a handful of symbols that name any cell, any candidate, and any logical link with total precision. The payoff is enormous - learn it and every advanced tutorial, forum post, and solver explanation suddenly opens up to you, because they all speak this same shorthand. It looks cryptic at first glance, all letters and numbers jammed together, but the whole system rests on just two simple ideas: a way to name a cell, and a way to name the link between two candidates. Master those and the rest is reading.
Naming cells and candidates
The backbone is the row-column reference. Rows are numbered one to nine from top to bottom, columns one to nine from left to right, and any cell is written as r then its row number, c then its column number. So r1c1 is the top-left corner, r9c9 the bottom-right, and r4c6 sits in row four, column six; you will also meet ranges like r1c123, meaning three cells in row one, columns one through three. A cell reference usually carries a value with it: 5r3c3 means the candidate five in row three, column three, the single atom that every chain is built from. When sudoku chain notation shows you 5r3c3 and 5r3c7, it is pointing at the same digit in two cells that share a row - exactly the kind of pair that forms a link. Say a few of these references aloud until the pattern feels automatic, because this grid reference is the foundation of all sudoku chain notation.
Reading strong and weak links
- Read each node as a candidate in a cell, written like 5r1c1.
- Read the connector between nodes: an equals sign is a strong link, a dash or hyphen is a weak link.
- A strong link means if one end is false the other must be true - both cannot be absent.
- A weak link means both cannot be true at once - if one is on, the other is off.
- Follow the alternation strong, weak, strong, weak from one end to the other; the two endpoints give the deduction.
Practising the language
The fastest way to internalise sudoku chain notation is to narrate your own moves in it while you play. Shapedoku uses nine shapes rather than digits, but the grid references work identically - r1c1 is still the top-left cell, and you can happily call the triangle shape one if you like a number to pin the notation to. Turn on Notes, play a Hard or Extreme board, and describe each link you find out loud as r-c plus strong or weak, tracing the alternation as you go. Within a few puzzles the symbols stop looking cryptic and start reading like plain sentences, and the deductions they encode become something you can see rather than decode. Every advanced sudoku chain notation guide you meet afterwards - and almost all serious technique writing uses it - becomes easy to follow, which quietly unlocks the entire library of hard-puzzle strategy that was previously closed to you.
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