1051. Height Checker

https://leetcode.com/problems/height-checker/

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
Example 3:
Input: heights = [1,2,3,4,5]
Output: 0

Constraints:
  • 1 <= heights.length <= 100
  • 1 <= heights[i] <= 100
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Intuition
Sort a copy of the array
Count how many elements are out of order
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Time - O(n log n)
Space - O(n)
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