1051. Height Checker

Problem

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

Problem Summary

When taking the annual school commemorative photo, students are generally required to stand in non-decreasing order of height. Please return the minimum number of students that must move so that all students are arranged in non-decreasing order of height. Note that when a group of students is selected, they can be reordered among themselves in any possible way, while the unselected students should remain in place.

Solution Approach

• Given an array of heights, output the minimum number of moves required to arrange this array in non-decreasing order of height.
• This is an easy problem. The minimum number of moves means that each move puts a student directly into their final position in one step. So use an auxiliary sorted array and compare the elements one by one to count.

Code

package leetcode

func heightChecker(heights []int) int {
	result, checker := 0, []int{}
	checker = append(checker, heights...)
	sort.Ints(checker)
	for i := 0; i < len(heights); i++ {
		if heights[i] != checker[i] {
			result++
		}
	}
	return result
}