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, at 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
nextwith a label in the range[curr + 1, min(curr + 6, n^2)]. - This choice simulates the result of a standard 6-sided die roll, so there are always at most
6destinations, regardless of the size of the board. - If
nexthas a snake or ladder, you must move to the destination of that snake or ladder. Otherwise, you move tonext. - The game ends when you reach square
n^2.
A board square on row r and column c has a snake or ladder if board[r][c] != -1. The destination of that snake or ladder is board[r][c]. Squares 1 and n^2 are not the starting points of any snake or ladder.
Note that you only take a snake or ladder at most once per dice roll. If the destination of a snake or ladder is the start of another snake or ladder, you do not follow the subsequent snake or ladder.
Return the least number of dice rolls required to reach square n^2. If it is not possible to reach the square, return -1.
-1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 35 -1 -1 13 -1 -1 -1 -1 -1 -1 -1 -1 15 -1 -1 -1 -1
board = [[-1,-1,-1,-1,-1,-1],[-1,-1,-1,-1,-1,-1],[-1,-1,-1,-1,-1,-1],[-1,35,-1,-1,13,-1],[-1,-1,-1,-1,-1,-1],[-1,15,-1,-1,-1,-1]]4-1 -1 -1 3
board = [[-1,-1],[-1,3]]1Constraints
- n == board.length == board[i].length
- 2 <= n <= 20
- board[i][j] is either -1 or in the range [1, n^2].
- The squares labeled 1 and n^2 are not the starting points of any snake or ladder.