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Java Solution for LeetCode algorithm problems, continually updating
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package g0901_1000.s0909_snakes_and_ladders;
// #Medium #Array #Breadth_First_Search #Matrix
// #2022_03_28_Time_7_ms_(79.52%)_Space_47.7_MB_(58.43%)
import java.util.LinkedList;
import java.util.Queue;
public class Solution {
private int size;
public int snakesAndLadders(int[][] board) {
Queue queue = new LinkedList<>();
size = board.length;
int target = size * size;
boolean[] visited = new boolean[target];
queue.add(1);
visited[0] = true;
int step = 0;
while (!queue.isEmpty()) {
int queueSize = queue.size();
for (int i = 0; i < queueSize; i++) {
int previousLabel = queue.poll();
if (previousLabel == target) {
return step;
}
for (int currentLabel = previousLabel + 1;
currentLabel <= Math.min(target, previousLabel + 6);
currentLabel++) {
if (visited[currentLabel - 1]) {
continue;
}
visited[currentLabel - 1] = true;
int[] position = indexToPosition(currentLabel);
if (board[position[0]][position[1]] == -1) {
queue.add(currentLabel);
} else {
queue.add(board[position[0]][position[1]]);
}
}
}
step++;
}
return -1;
}
private int[] indexToPosition(int index) {
int vertical = this.size - 1 - (index - 1) / this.size;
int horizontal;
if ((this.size - vertical) % 2 == 1) {
horizontal = (index - 1) % this.size;
} else {
horizontal = this.size - 1 - (index - 1) % this.size;
}
return new int[] {vertical, horizontal};
}
}