[LeetCode] 1051. Height Checker 身高检查器

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

这道题说是有一群学生随机的站成一排照相，现在想让学生按照身高来排列，问需要移动
多个同学。这是一道很简单的题目没有什么难度，只要复制一个新的数组，然后给数组排序，再跟原数组逐个按数字来对比，只要数字不同，则结果 res 自增1即可，参见代码如下：

class Solution {
public:
	int heightChecker(vector<int>& heights) {
		int res = 0, n = heights.size();
		vector<int> sorted = heights;
		sort(sorted.begin(), sorted.end());
		for (int i = 0; i < n; ++i) {
		  	if (sorted[i] != heights[i]) ++res;
		}
		return res;
	}
};

Github 同步地址:

https://github.com/grandyang/leetcode/issues/1051

参考资料：

https://leetcode.com/problems/height-checker/

https://leetcode.com/problems/height-checker/discuss/299221/C%2B%2B-Sort

https://leetcode.com/problems/height-checker/discuss/299216/Java-Sort-1ms-O(nlogn)

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