2579

theforestvn88 · theforestvn88 · commit e5a36d64dcdf · 2025-03-05T17:02:56.000+07:00
diff --git a/2501-2600/2579_count_total_number_of_colored_cells.rb b/2501-2600/2579_count_total_number_of_colored_cells.rb
@@ -0,0 +1,10 @@
+# @param {Integer} n
+# @return {Integer}
+def colored_cells(n)
+    # from top cell to the mid line
+    # count = 1 + 3 + 5 + ... + (2n - 1) = n**2
+    # the same as from bottom cell to the mid line
+    # but the mid line is duplicate
+    # so 2 * count - the-mid-line-count
+    2 * n**2 - (2*n - 1)
+end
