In each row and column, you must step on exactly the number of squares dictated by that row or column. So, because the leftmost column is numbered 1, and you start in the top square of that column, you can never step into that column again. Also, as with all mazes, you cannot cross your own path.
1 4 4 1 4 4 7 1 3 7 1 7 +---+---+---+---+---+---+---+---+---+---+---+---+ | | | | | | | | | | | | | 9 +---+---+---+---+---+---+---+---+---+---+---+---+ | | | | | | | | | | | | | 7 +---+---+---+---+---+---+---+---+---+---+---+---+ | | | | | | | | | | | | | 6 +---+---+---+---+---+---+---+---+---+---+---+---+ | | | | | | | | | | | | | 5 +---+---+---+---+---+---+---+---+---+---+---+---+ | | | | | | | | | | | | | 7 +---+---+---+---+---+---+---+---+---+---+---+---+ | | | | | | | | | | | | | 4 +---+---+---+---+---+---+---+---+---+---+---+---+ | | | | | | | | | | | | | 6 +---+---+---+---+---+---+---+---+---+---+---+---+