Word Sudoku

Solve it as sudoku, not as a word

The mistake almost everyone makes with Word Sudoku is treating it like an anagram. You see nine letters and your brain immediately tries to rearrange them into the hidden word. Resist that. The nine letters are just symbols standing in for the digits one through nine, and every technique that cracks an ordinary sudoku works here untouched. Scan each row, column, and 3x3 box for a letter that can only go in one spot. Hunt for cells where eight of the nine letters are already ruled out. The alphabet on the tiles changes nothing about the logic.

What does help is remembering that the letters have no order. There is no sense in which a comes before b on this grid, so do not let the familiar sequence pull you into false assumptions. Pencil in candidates exactly as you would with numbers. And borrow the other habit good number players have: work where the information is. A box with seven letters placed will hand you the last two almost for free, while a nearly empty box gives you nothing however long you stare at it. Finish the crowded regions first and let them feed the empty ones.

Three moves that carry you

Three standard sudoku moves do most of the work here, and they all translate straight into letters. The first is the sweep, which solvers call cross-hatching: pick a letter that already appears often, say the T in a grid built on the letters of EDUCATION, and trace the rows and columns it occupies. Any box still missing a T must take one in a cell those lines do not touch, and often only one cell survives the crossfire. The second is the fill-in count: find the row, column, or box with the most letters already placed, list the few that are missing, and test each empty cell against its own column and box. With only two letters missing this is usually instant. The third is the single: a cell where eight letters are ruled out has no choice left, and every one you fill powers the next sweep. Rotate through the three and the grid falls without any word knowledge at all. Pencil marks help more here than in number sudoku, simply because letters are harder to hold in your head. Jot the candidates in a cell's corner and cross them off as your sweeps land.

Using the hidden word

The bonus is the payoff for solving, but it can also be a lever. Since one line (a row, column, or diagonal, depending on the puzzle) is meant to spell a real nine-letter word, a few confirmed letters in that line can sometimes let you guess the whole word and drop five or six letters at once. That is a big shortcut in a puzzle that otherwise gives you no numbers to lean on. If you are stuck two-thirds of the way through, read the special line and see whether a word suggests itself.

Just be careful: guessing the word too early, on only two or three letters, can send you down a wrong path that takes ages to unwind. Trust the word only when the grid has already narrowed it.

Where it comes from

This variant is often printed as Wordoku in newspapers and puzzle books, and the number version behind it has a neat pedigree. A retired American architect named Howard Garns invented the modern puzzle in 1979 for Dell puzzle magazines, under the plain name Number Place. The Japanese publisher Nikoli picked it up in 1984, gave it the snappier name Sudoku, and made it a national habit. Then a retired judge named Wayne Gould spent years writing a program to generate puzzles and talked The Times of London into printing one in late 2004, and within a year the grid was in papers on every continent. Letter versions followed almost immediately, partly for variety and partly because hiding a word in the grid hands finishers a small extra prize. The logic never changed along the way. Whether the symbols are digits or the nine letters of a word, it is the same tidy machine, and it is timed here, so calm scanning beats frantic guessing.