### Puzzle Week, Day 7: Kakuro

I saved my favorite puzzle for last. Kakuro is said to be a mix of Sudoku and Crossword puzzles. It has logic similar to Sudoku, but with math added to it. The idea is to fill rows and columns with the specified sums using the numbers from 1 to 9 and without repeating a number in that column or row. A sample Kakuro puzzle and solution are below:

I find Kakuro puzzles challenging, but very fun. They really help you work on your math. That is, unless you use combinations cheat sheets, which really take the fun out of it and makes it loose its purpose. First time I tried Kakuro, it took me about 45 minutes to finish an easy one. After a while, I managed to get the time down for easy ones to around 5 minutes. Now I am back to about an hour of solving time tackling a book called "Black Belt Kakuro", which is the hardest out of a series of four Kakuro books. My challenge is trying to solve them without annotating possibilities in the cells, that is, only writing in a cell when I have the answer. Kakuro really is a great puzzle. If there is one puzzle book that you buy in the whole year, be sure to make it Kakuro. Happy solving!