Puzzle  Can a Knight reach bottom from top by visiting all squares
Puzzle
Is there a way for a chess knight to start at the topleft corner from a N x N chessboard, visit all the squares of the board exactly once and end at the lowerright corner.
Solution
We need to traverse all the squares of the chessboard exactly once. Also, the moves of the knight are Lshaped, that is, traverse two squares vertically or horizontally. A simple observation to take from this is that in one move, the knight starts and ends at two different colored squares.
Consider two cases:

Case N is even: Let the value of N be 8. Hence, total number of squares on the board will be 64. Now, to visit all the squares of the board exactly once the knight would have to make 63 moves. Since, total number of moves are odd, the journey will start and end on the squares of the opposite color. Since, the squares on the topleft corner and lowerright corner are both coloured the same, hence the journey is impossible.

Case N is odd: Let the value of N be 9. Hence, total number of squares on the board will be 81. Now, to visit all the squares of the board exactly once the knight would have to make 80 moves. Since, total number of moves are even, the journey will start and end on the squares of the same color. Since, the squares on the upperleft corner and lowerright corner are of the same color, hence the journey on 9 x 9 board is possible.
Hence, on a N x N chessboard, a knight will have to make (N^{2} – 1) moves to visit each square exactly once. So, if N is even, the journey is impossible and for odd values of N, the journey is possible.
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