1051. Height Checker

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

Rust Solution

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);
}

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