17- Skyscrapers

Skyscrapers

(Published in Czech Republic Academic Championship)

Write a single number from 1 to 9 in each cell such that each number appears exactly once in every row, column and bolded 3x3 box. The numbers outside the grid means how many skyscrapers are seen from that direction of particular row or column (higher skyscrapers cover lower ones behind them).

16- Mathdoku

Mathdoku

(Published in Czech Republic Academic Championship)

Write a single number from 1 to 9 in each cell such that each number appears exactly once in every row, column and bolded 3x3 box. For more, in each of nine nonets (3x3 squares) there are subsidiary numbers between two cells. These numbers are the results of binary operations (addition, subtraction, multiplication, or division) between the two cells. In each nonet there must be used all the four binary operations.

14- X-Sums Sudoku

X-Sums Sudoku

(Published in Czech Republic Academic Championship)

Place a digit from 1 to 9 into each of the empty squares so that each digit appears exactly once in each of the rows, columns and the irregularly shaped regions. The numbers outside the grid represent the sum of the first X digits in the respective row or column, with X being the digit in the first cell of that row or column.

11- Straight Sudoku

Straight Sudoku

(Published in Czech Republic Academic Championship)

Place a digit from 1 to 9 into each of the empty squares so that each digit appears exactly once in each row, column and 3x3 box. Moreover, the indicated lines in the grid should contain straight consecutive digits (e.g. 1-2-3-4, not 1-2-3-2!). Where there is no indicated line there can't be any straight horizontal, vertical or diagonal line which contains more than 2 consecutive numbers.