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ShortestPathInBinaryMatrix.java
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ShortestPathInBinaryMatrix.java
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package Leetcode;
import java.util.LinkedList;
import java.util.Queue;
/**
* @author kalpak
*
* Given an n x n binary matrix grid, return the length of the shortest clear path in the matrix.
* If there is no clear path, return -1.
*
* A clear path in a binary matrix is a path from the top-left cell
* (i.e., (0, 0)) to the bottom-right cell (i.e., (n - 1, n - 1)) such that:
*
* All the visited cells of the path are 0.
* All the adjacent cells of the path are 8-directionally connected (i.e., they are different and they share an edge or a corner).
* The length of a clear path is the number of visited cells of this path.
*
*
* Example 1:
* Input: grid = [[0,1],[1,0]]
* Output: 2
*
*
* Example 2:
* Input: grid = [[0,0,0],[1,1,0],[1,1,0]]
* Output: 4
*
*
* Example 3:
* Input: grid = [[1,0,0],[1,1,0],[1,1,0]]
* Output: -1
*
*
* Constraints:
* n == grid.length
* n == grid[i].length
* 1 <= n <= 100
* grid[i][j] is 0 or 1
*
*/
public class ShortestPathInBinaryMatrix {
public static int shortestPathBinaryMatrix(int[][] grid) {
if(grid[0][0] == 1)
return -1;
int[][] dirs = {{-1,-1},{-1,0},{-1,1},{0,-1},{0,0},{0,1},{1,-1},{1,0},{1,1}};
Queue<int []> q = new LinkedList<>();
boolean[][] isVisited = new boolean[grid.length][grid.length];
int result = 0;
if(grid[0][0] == 0)
q.add(new int[]{0,0});
int count =1;
while(!q.isEmpty()) {
int size = q.size();
count = 0;
result++;
for(int i = 0;i < size; i++) {
int point[] = q.poll();
int x1 = point[0];
int y1 = point[1];
if(isVisited[x1][y1]==true)
continue;
if(x1 == grid.length - 1 && y1 == grid.length - 1)
return result;
isVisited[x1][y1] = true;
for(int[] dir : dirs) {
int x = x1 + dir[0];
int y = y1 + dir[1];
if(x < 0 || y < 0 || x >= grid.length || y >= grid.length || isVisited[x][y] == true || grid[x][y] == 1)
continue;
else {
q.add(new int[]{x,y});
count++;
}
}
}
}
return -1;
}
public static void main(String[] args) {
int[][] grid = new int[][]{{0,0,0}, {1,1,0}, {1,1,0}};
System.out.println("The distance of the shortest path in the binary matrix is : " + shortestPathBinaryMatrix(grid));
}
}