1727-largest-submatrix-with-rearrangements.rb

# 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}
deflargest_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|
ifmatrix[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"
classTest_largest_submatrix < Test::Unit::TestCase
deftest_
assert_equal4,largest_submatrix([[0,0,1],[1,1,1],[1,0,1]])
assert_equal3,largest_submatrix([[1,0,1,0,1]])
assert_equal2,largest_submatrix([[1,1,0],[1,0,1]])
end
end