題目
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
分析
題意：給定一個數組，返回將其升序排序所需的最小移動步數。
腦筋急轉彎！
事實上我們只需要比較排序前和排序後對應位置的數不同的個數即可。
比如
14235 排序得到12345
相同位置不同數的個數爲3
解答
class Solution {
public int heightChecker(int[] heights) {
// 備份一個未排序的
int[] tmp = Arrays.copyOf(heights,heights.length);
// 排序
Arrays.sort(heights);
int res=0;
// 求出不同的個數
for(int i=0;i<heights.length;++i){
if(tmp[i]!=heights[i]) res++;
}
return res;
}
}