1727. Largest Submatrix With Rearrangements (#168)

Author: remy727

README.md

@@ -389,6 +389,7 @@
 | 1697 | Checking Existence of Edge Length Limited Paths | [Ruby](./algorithms/ruby/1697-checking-existence-of-edge-length-limited-paths.rb) | Hard |
 | 1706 | Where Will the Ball Fall | [Ruby](./algorithms/ruby/1706-where-will-the-ball-fall.rb) | Medium |
 | 1721 | Swapping Nodes in a Linked List | [Ruby](./algorithms/ruby/1721-swapping-nodes-in-a-linked-list.rb) | Medium |
+| 1727 | Largest Submatrix With Rearrangements | [Ruby](./algorithms/ruby/1727-largest-submatrix-with-rearrangements.rb) | Medium |
 | 1732 | Find the Highest Altitude | [Ruby](./algorithms/ruby/1732-find-the-highest-altitude.rb) | Easy |
 | 1743 | Restore the Array From Adjacent Pairs | [Ruby](./algorithms/ruby/1743-restore-the-array-from-adjacent-pairs.rb) | Medium |
 | 1751 | Maximum Number of Events That Can Be Attended II | [Ruby](./algorithms/ruby/1751-maximum-number-of-events-that-can-be-attended-ii.rb) | Hard |

algorithms/ruby/1727-largest-submatrix-with-rearrangements.rb

@@ -0,0 +1,79 @@
+# frozen_string_literal: true
+
+# 1727. Largest Submatrix With Rearrangements
+# Medium
+# https://leetcode.com/problems/largest-submatrix-with-rearrangements
+
+=begin
+You are given a binary matrix matrix of size m x n, and you are allowed to rearrange the columns of the matrix in any order.
+Return the area of the largest submatrix within matrix where every element of the submatrix is 1 after reordering the columns optimally.
+
+Example 1:
+Input: matrix = [[0,0,1],[1,1,1],[1,0,1]]
+Output: 4
+Explanation: You can rearrange the columns as shown above.
+The largest submatrix of 1s, in bold, has an area of 4.
+
+Example 2:
+Input: matrix = [[1,0,1,0,1]]
+Output: 3
+Explanation: You can rearrange the columns as shown above.
+The largest submatrix of 1s, in bold, has an area of 3.
+
+Example 3:
+Input: matrix = [[1,1,0],[1,0,1]]
+Output: 2
+Explanation: Notice that you must rearrange entire columns, and there is no way to make a submatrix of 1s larger than an area of 2.
+
+Constraints:
+m == matrix.length
+n == matrix[i].length
+1 <= m * n <= 105
+matrix[i][j] is either 0 or 1.
+=end
+
+# @param {Integer[][]} matrix
+# @return {Integer}
+def largest_submatrix(matrix)
+  m = matrix.size
+  n = matrix[0].size
+  columns = Array.new(m) { [] }
+
+  0.upto(n - 1) do |j|
+    seq = 0
+
+    (m - 1).downto(0) do |i|
+      if matrix[i][j] == 1
+        seq += 1
+        columns[i][j] = seq
+      else
+        seq = 0
+      end
+    end
+  end
+
+  max = 0
+
+  0.upto(m - 1) do |i|
+    cols = columns[i].compact.sort
+    n = cols.size
+    (n - 1).downto(0) do |j|
+      max = [max, (n - j) * cols[j]].max
+    end
+  end
+
+  max
+end
+
+# **************** #
+#       TEST       #
+# **************** #
+
+require "test/unit"
+class Test_largest_submatrix < Test::Unit::TestCase
+  def test_
+    assert_equal 4, largest_submatrix([[0, 0, 1], [1, 1, 1], [1, 0, 1]])
+    assert_equal 3, largest_submatrix([[1, 0, 1, 0, 1]])
+    assert_equal 2, largest_submatrix([[1, 1, 0], [1, 0, 1]])
+  end
+end