Height Checker

Description

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

Code

Java

public int heightChecker(int[] heights) {
    int[] temp = new int[heights.length];
    int count = 0;
    System.arraycopy(heights, 0, temp, 0, heights.length);
    Arrays.sort(heights);
    for (int i = 0; i < heights.length; i++) {
        if (heights[i] != temp[i]) {
            count++;
        }
    }
    return count;
}

Java

public int heightChecker(int[] heights) {
    int[] heightToFreq = new int[101];
    for (int height : heights) {
        heightToFreq[height]++;
    }
    int result = 0;
    int curHeight = 0;
    for (int height : heights) {
        while (heightToFreq[curHeight] == 0) {
            curHeight++;
        }
        if (curHeight != height) {
            result++;
        }
        heightToFreq[curHeight]--;
    }
    return result;
}