search_a_2d_matrix_ii.rb

# https://leetcode.com/problems/search-a-2d-matrix-ii/
#
# Write an efficient algorithm that searches for a value in an m x n matrix.
# This matrix has the following properties:
#
#     + Integers in each row are sorted in ascending from left to right.
#     + Integers in each column are sorted in ascending from top to bottom.
#
# For example:
#
#     Consider the following matrix:
#
#         [
#           [1,   4,  7, 11, 15],
#           [2,   5,  8, 12, 19],
#           [3,   6,  9, 16, 22],
#           [10, 13, 14, 17, 24],
#           [18, 21, 23, 26, 30]
#         ]
#
#     Given target = 5, return true.
#     Given target = 20, return false.


# @param {Integer[][]} matrix
# @param {Integer} target
# @return {Boolean}
def search_matrix(matrix, target)
  return false if matrix.empty?

  m, n = matrix.size, matrix[0].size
  i, j = 0, n - 1
  while i != m && j != -1
    case matrix[i][j] <=> target
    when -1; i += 1
    when  0; return true
    when  1; j -= 1
    end
  end
  return false
end