lee_algo.js

// https://repl.it/CCAm/2

"use strict";

var map = 
`.....
.....
.###.
.....
.....`.split("\n");

var w = map[0].length, h = map.length;

function is_good_coord(x, y) {
	return x >= 0 && x < w && y >= 0 && y < h;
}

function is_floor(x, y) {
	return map[y][x] == '.';
}

function is_movable(x, y) {
	return is_good_coord(x, y) && is_floor(x, y);
}

var dxdy = [[1, 1], [1, 0], [1, -1], [0, 1], [0, -1], [-1, 1], [-1, 0], [-1, -1]];
function bfs (x1, y1) {
	var q = [[x1, y1, 0]], used = [], grid = [];
	for (var i=0; i<h; i++) {
		used[i] = [];
		grid[i] = new Array(w);
		grid[i].fill(-1);
	}
	used[y1][x1] = true;
	while (q.length > 0) {
		var [x, y, d] = q.shift();
		grid[y][x] = d;
		for (var [dx, dy] of dxdy) {
			var tx = x + dx, ty = y + dy;
			if (is_movable(tx, ty) && !used[ty][tx]) {
				used[ty][tx] = true;
				q.push([tx, ty, d+1]);
			}
		}
	}
	return grid;
}

console.log(bfs(0, 0));

function lee (x1, y1, x2, y2) {
	var grid = bfs(x1, y1);
	if (grid[y2][x2] < 0) return;
	var [x, y] = [x2, y2], d = grid[y2][x2];
	while (d > 0) {
		d -= 1;
		
	}
}