Given a matrix, find the shortest distance from a source cell to a destination cell, traversing through limited cells only. Can move only up, down, left and right. If found output the distance else -1.

ShortestDistanceBetweenTwoCells.java

import java.util.*;
import java.lang.*;
import java.io.*;


class ShortestDistanceBetweenTwoCells {

	static class Cell {

		int row;
		int col;
		int distance;

		Cell(int x, int y, int d) {
			this.row = x;
			this.col = y;
			this.distance = d;
		}

	}

	static Queue<Cell> queue = new LinkedList<>();

	static int shortestDistance(char[][] matrix) {

		Cell source = new Cell(0,0,0);
		int matrixRows = matrix.length;
		int matrixCols = matrix[0].length;

		boolean[][] visited = new boolean[matrixRows][matrixCols];

		for (int i = 0; i < matrixRows; i++) {
			for (int j = 0; j < matrixCols; j++) {
				if (matrix[i][j] == 'x') {
					visited[i][j] = true;
				} else if (matrix[i][j] == 's') {
					source.row = i;
					source.col = j;
				} else {
					visited[i][j] = false;
				}
			}
		}

		queue.add(source);
		visited[source.row][source.col] = true;

		while (!queue.isEmpty()) {

			Cell item = queue.poll();

			if (matrix[item.row][item.col] == 'd')
				return item.distance;

			// move down
			if (item.row+1 < matrixRows  &&  !visited[item.row + 1][item.col]) {
				queue.add(new Cell(item.row+1, item.col, item.distance+1));
				visited[item.row+1][item.col] = true;
			}

			// move up
			if (item.row-1 >= 0  &&  !visited[item.row - 1][item.col]) {
				queue.add(new Cell(item.row-1, item.col, item.distance+1));
				visited[item.row-1][item.col] = true;
			}
			
			// move right
			if (item.col+1 < matrixCols  &&  !visited[item.row][item.col+1]) {
				queue.add(new Cell(item.row, item.col+1, item.distance+1));
				visited[item.row][item.col+1] = true;
			}
			
			// move left
			if (item.col-1 >= 0  &&  !visited[item.row][item.col-1]) {
				queue.add(new Cell(item.row, item.col-1, item.distance+1));
				visited[item.row][item.col-1] = true;
			}

		}

		return -1;

	}

	public static void main(String[] args) {

		/*
		 * s - source
		 * d - destination
		 * . - path
		 * x - wall
		 */
		
		char[][] grid = { { 'x', 's', '.', '.' },
                          { 'x', 'x', '.', '.' },
                          { '.', '.', '.', 'x' },
                          { '.', 'x', 'x', 'x' },
                          { '.', '.', '.', 'd' } };

        System.out.println(shortestDistance(grid));

	}

}