The Kakuro Challenge 1

There are various levels of difficulty in the book and the malicious ones are really malicious (but fun!). I don't like things to be labeled hard to find out they really aren't - that is not the case here - you need to work at them. I have bought two copies of this book and gave one to my brother-in-law.

This book presents us with a graded series of kakuro challenges. The introduction is quite clear on strategy, although the Divide and Conquer section has a few paragraphs that hopefully will be corrected in later editions. However, Chisolm looks only at the case where a single digit has been discovered. As with Sudoku, a very useful tactic focuses on discovering pairs of cells that must choose from the same two candidates. In Kakuro one may sum the two choices and subtract from the block total to give information about the other cells. Similarly for three cells with three candidates, etc. The challenges are presented in four levels of difficulty. The first level problems are presented on an 8 by 8 grid, the longest blocks are of length 5. The second level grids are 10 by 10. The third level are on a 10 by 12 grid, with some blocks of length 6. The fourth level are also on 10 by 12 grids, with a few length 7 blocks. There are no length 8 or length 9 blocks. It is possible to do the first level in ink, without having to record intermediate guesses. The proper choices are pretty much locally determined by the situation in blocks not more than two or three cells away. This is not true of later levels, in which some choices require resolution of situations at more distant cells. A good pencil and eraser is essential. I worked through all 201 puzzles and found the book to be effective in acquiring improved facility.