Semi ordered permutation

Array Simulation

64.1% acceptance

Feb 25, 2026

228

You are given a 0-indexed permutation of n integers nums. A permutation is called semi-ordered if the first number equals 1 and the last number equals n. You can perform the below operation as many times as you want until you make nums a semi-ordered permutation: Pick two adjacent elements in nums, then swap them. Return the minimum number of operations to make nums a semi-ordered permutation.

Solution

Rust

Time O(n)

Space O(1)

LeetCode

solution.rs

impl Solution {
  pub fn semi_ordered_permutation(nums: Vec<i32>) -> i32 {
    let n = nums.len();
    let idx1 = nums.iter().position(|&x| x == 1).unwrap();
    let idxn = nums.iter().position(|&x| x == n as i32).unwrap();
    let mut ops = idx1 + (n - 1 - idxn);
    if idx1 > idxn { ops -= 1; }
    ops as i32
  }
}