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SnakesAndLadders.java
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SnakesAndLadders.java
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package Leetcode;
import java.util.LinkedList;
import java.util.Queue;
/**
* @author kalpak
*
*
*/
public class SnakesAndLadders {
public static int snakesAndLadders(int[][] board) {
if(board == null || board.length == 0 )
return -1;
int len = board.length;
boolean[] isVisited = new boolean[len * len + 1];
Queue<Integer> queue = new LinkedList<>();
int moves = 0;
int result = len*len;
// Start at 1
queue.offer(1);
while(!queue.isEmpty()) {
int size = queue.size();
for(int i = 0; i < size; i++) {
int currentPosition = queue.poll();
if(currentPosition == len*len) // reached the end
result = Math.min(result, moves);
for(int j = 1; j <= 6; j++) {
int possibleMove = currentPosition + j;
if(possibleMove > len*len)
break;
if(!isVisited[possibleMove]) {
isVisited[possibleMove] = true;
int row = len - (possibleMove - 1) / len - 1;
int col = (len - row) % 2 == 0 ? len - (possibleMove - 1) % len - 1 : (possibleMove - 1) % len;
if(board[row][col] == currentPosition)
continue;
if(board[row][col] == -1)
queue.offer(possibleMove);
else
queue.offer(board[row][col]);
}
}
}
moves++;
}
return result == len*len ? -1 : result;
}
public static void main(String[] args) {
int[][] board = new int[][]{{-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}};
System.out.println("The minimum number of moves needs to reach the end : " + snakesAndLadders(board));
}
}