Determine if a Cell Is Reachable at a Given Time

README.md

@@ -446,6 +446,7 @@
 | 2697 | Lexicographically Smallest Palindrome | [Ruby](./algorithms/ruby/2697-lexicographically-smallest-palindrome.rb) | Easy |
 | 2707 | Extra Characters in a String | [Ruby](./algorithms/ruby/2707-extra-characters-in-a-string.rb) | Medium |
 | 2742 | Painting the Walls | [Ruby](./algorithms/ruby/2742-painting-the-walls.rb) | Hard |
+| 2849 | Determine if a Cell Is Reachable at a Given Time | [Ruby](./algorithms/ruby/2849-determine-if-a-cell-is-reachable-at-a-given-time) | Medium |
 
 ### Database
 | # | Title | Solution | Difficulty |

algorithms/ruby/2849-determine-if-a-cell-is-reachable-at-a-given-time.rb

@@ -0,0 +1,50 @@
+# frozen_string_literal: true
+
+# 2849. Determine if a Cell Is Reachable at a Given Time
+# Medium
+# https://leetcode.com/problems/determine-if-a-cell-is-reachable-at-a-given-time
+
+=begin
+You are given four integers sx, sy, fx, fy, and a non-negative integer t.
+In an infinite 2D grid, you start at the cell (sx, sy). Each second, you must move to any of its adjacent cells.
+Return true if you can reach cell (fx, fy) after exactly t seconds, or false otherwise.
+A cell's adjacent cells are the 8 cells around it that share at least one corner with it. You can visit the same cell several times.
+
+Example 1:
+Input: sx = 2, sy = 4, fx = 7, fy = 7, t = 6
+Output: true
+Explanation: Starting at cell (2, 4), we can reach cell (7, 7) in exactly 6 seconds by going through the cells depicted in the picture above.
+
+Example 2:
+Input: sx = 3, sy = 1, fx = 7, fy = 3, t = 3
+Output: false
+Explanation: Starting at cell (3, 1), it takes at least 4 seconds to reach cell (7, 3) by going through the cells depicted in the picture above. Hence, we cannot reach cell (7, 3) at the third second.
+
+Constraints:
+* 1 <= sx, sy, fx, fy <= 109
+* 0 <= t <= 109
+=end
+
+# @param {Integer} sx
+# @param {Integer} sy
+# @param {Integer} fx
+# @param {Integer} fy
+# @param {Integer} t
+# @return {Boolean}
+def is_reachable_at_time(sx, sy, fx, fy, t)
+ return false if t == 1 && sx == fx && sy == fy
+
+ (sx - fx).abs <= t && (sy - fy).abs <= t
+end
+
+# **************** #
+# TEST #
+# **************** #
+
+require "test/unit"
+class Test_is_reachable_at_time < Test::Unit::TestCase
+ def test_
+ assert_equal true, is_reachable_at_time(2, 4, 7, 7, 6)
+ assert_equal false, is_reachable_at_time(3, 1, 7, 3, 3)
+ end
+end