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Java-based LeetCode algorithm problem solutions, regularly updated

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package g1001_1100.s1051_height_checker;

// #Easy #Array #Sorting #Counting_Sort #2022_02_28_Time_1_ms_(94.01%)_Space_42.6_MB_(5.71%)

/**
 * 1051 - Height Checker\.
 *
 * Easy
 *
 * A school is trying to take an annual photo of all the students. The students are asked to stand in a single file line in **non-decreasing order** by height. Let this ordering be represented by the integer array `expected` where `expected[i]` is the expected height of the i^th student in line.
 *
 * You are given an integer array `heights` representing the **current order** that the students are standing in. Each `heights[i]` is the height of the i^th student in line ( **0-indexed** ).
 *
 * Return _the **number of indices** where_ `heights[i] != expected[i]`.
 *
 * **Example 1:**
 *
 * **Input:** heights = [1,1,4,2,1,3]
 *
 * **Output:** 3
 *
 * **Explanation:**
 *
 * heights: [1,1,4,2,1,3]
 *
 * expected: [1,1,1,2,3,4]
 *
 * Indices 2, 4, and 5 do not match.
 *
 * **Example 2:**
 *
 * **Input:** heights = [5,1,2,3,4]
 *
 * **Output:** 5
 *
 * **Explanation:**
 *
 * heights: [5,1,2,3,4]
 *
 * expected: [1,2,3,4,5]
 *
 * All indices do not match.
 *
 * **Example 3:**
 *
 * **Input:** heights = [1,2,3,4,5]
 *
 * **Output:** 0
 *
 * **Explanation:**
 *
 * heights: [1,2,3,4,5]
 *
 * expected: [1,2,3,4,5]
 *
 * All indices match.
 *
 * **Constraints:**
 *
 * *   `1 <= heights.length <= 100`
 * *   `1 <= heights[i] <= 100`
**/
public class Solution {
    public int heightChecker(int[] heights) {
        int heightDiff = 0;
        int[] count = new int[101];
        int[] actualLine = new int[heights.length];
        for (int height : heights) {
            count[height]++;
        }
        int heightLength = 0;
        for (int i = 0; i < count.length; i++) {
            if (count[i] > 0) {
                for (int j = 0; j < count[i]; j++) {
                    actualLine[heightLength] = i;
                    heightLength++;
                }
                count[i] = 0;
            }
        }
        for (int i = 0; i < heights.length; i++) {
            if (actualLine[i] != heights[i]) {
                heightDiff++;
            }
        }
        return heightDiff;
    }
}