312. Snakes and Ladders

You are given an n x n integer matrix board where the cells are labeled from 1 to n^2 in a Boustrophedon style starting from the bottom left of the board (i.e. board[n - 1][0]) and alternating direction each row. You start on square 1 of the board. In each move, starting from square curr, do the following: - Choose a destination square next with a label in the range [curr + 1, min(curr + 6, n^2)]. - If next has a snake or ladder, you must move to the destination of that snake or ladder. Otherwise, you move to next. The game ends when you reach the square n^2. A board square on row r and column c has a snake or ladder if board[r][c] != -1. Return the least number of moves required to reach the square n^2. If it is not possible to reach the square, return -1.