heightChecker.py

"""
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.

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.
"""

class Solution:
    def heightChecker(self, heights: List[int]) -> int:
        sortedh = sorted(heights)
        count = 0
        for i in range(len(heights)):
            if sortedh[i] != heights[i]:
                count += 1
        return count

# Time Complexity = O(nlogn)
# Space Complexity = O(n)