1051. Height Checker

문제

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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Solution

class Solution {
    public int heightChecker(int[] heights) {
        int[] unsorted = new int[heights.length];
        
        for (int i = 0; i < heights.length; i++){
            unsorted[i] = heights[i];
        }
        
        Arrays.sort(heights);
        int count = 0;
        
        for(int i = 0; i < heights.length; i++){
            if(heights[i] != unsorted[i]) count++;
        }
        
        return count;
    }
}