LeetCode： Height Checker

Question

Students are asked to stand in non-decreasing order of heights for an annual photo.

Return the minimum number of students that must move in order for all students to be standing in non-decreasing order of height.

Notice that when a group of students is selected they can reorder in any possible way between themselves and the non selected students remain on their seats.

Example 1:

Input: heights = [1,1,4,2,1,3]

Output: 3

Explanation:

Current array : [1,1,4,2,1,3]

Target array : [1,1,1,2,3,4]

On index 2 (0-based) we have 4 vs 1 so we have to move this student.

On index 4 (0-based) we have 1 vs 3 so we have to move this student.

On index 5 (0-based) we have 3 vs 4 so we have to move this student.

Example 2:

Input: heights = [5,1,2,3,4]

Output: 5

Solution #1

def height_checker(heights)
  counter = 0
  sorted_heights = heights.sort

  sorted_heights.each_with_index do |height, index|
    counter += 1 if heights[index] != height
  end
  counter
end

Solution #2

def height_checker(heights)
  counter = 0
  heights.sort.each_with_index { |height,index| counter += 1 if height != heights[index] }
  counter
end