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:3Explanation: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`

```
struct Solution;
impl Solution {
fn height_checker(heights: Vec<i32>) -> i32 {
let mut sorted = heights.to_vec();
sorted.sort_unstable();
heights
.iter()
.zip(sorted.iter())
.fold(0, |sum, (a, b)| if a != b { sum + 1 } else { sum })
}
}
#[test]
fn test() {
let heights = vec![1, 1, 4, 2, 1, 3];
assert_eq!(Solution::height_checker(heights), 3);
}
```