>Since this interviewer seems to have made up their mind already with pre-conceptions of which candidate is worth hiring, what is the "correct" answer to this question? "Pick random co-ordinates, check, and retry?"
The most efficient way (which is arguably unnecessary for Minesweeper) is to treat a 10x10 play field as a 1 dimensional array of size 100, stick your X number of mines in the first X cells in the array, then use something like the Fisher-Yates shuffle* on the array.
* Y = random number 1-100. Swap contents of cell Y and cell 100. Y = random number 1-99, swap contents of cell Y and cell 99. Repeat for entire array.
The most efficient way (which is arguably unnecessary for Minesweeper) is to treat a 10x10 play field as a 1 dimensional array of size 100, stick your X number of mines in the first X cells in the array, then use something like the Fisher-Yates shuffle* on the array.
* Y = random number 1-100. Swap contents of cell Y and cell 100. Y = random number 1-99, swap contents of cell Y and cell 99. Repeat for entire array.