1051. Height Checker

Posted 2020-12-13 whatyouthink

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.

这题的差评率非常高，因为描述和题目本身的意思严重不符合，他的本意是求有多少个人不在对应的位置上，而不是题目描述中所谓的最少需要移动多少个学生使得身高不递减。

比如[1,2,4,3]这个case，答案是2.所以根本不是题目描述的那样，否则答案是1,3和4掉换就完事了

这题本质是求有多少学生位置和排序后是不一致的

• 1 <= heights.length <= 100
• 1 <= heights[i] <= 100

可以nlog排序然后比较diff

也可以o(m) 基数排序，m是数的大小，然后按顺序去diff

class Solution(object):
    def heightChecker(self, heights):
        """
        :type heights: List[int]
        :rtype: int
        """
        count = [0] * 101
        for value in heights:
            count[value] += 1
        index = 0
        ans = 0
        for i in range(101):
            if count[i] == 0:
                continue
            while count[i] > 0:
                if i != heights[index]:
                    ans += 1
                count[i] -= 1
                index += 1
        return ans