Minimum deletions to make array beautiful

Array Stack Greedy

49.8% acceptance

Feb 25, 2026

835

You are given a 0-indexed integer array nums. The array nums is beautiful if: nums.length is even. nums[i] != nums[i + 1] for all i % 2 == 0. Note that an empty array is considered beautiful. You can delete any number of elements from nums. When you delete an element, all the elements to the right of the deleted element will be shifted one unit to the left to fill the gap created and all the elements to the left of the deleted element will remain unchanged. Return the minimum number of elements to delete from nums to make it beautiful.

Solution

Rust

Time O(n)

Space O(1)

LeetCode

solution.rs

impl Solution {
  pub fn min_deletion(nums: Vec<i32>) -> i32 {
    let mut del = 0i32;
    let mut parity = 0; // 0 = next position is even, 1 = next is odd
    let mut last_even = -1i32;
    for &x in &nums {
      if parity == 0 {
        last_even = x;
        parity = 1;
      } else if x == last_even {
        del += 1; // delete this element, stay at parity 1
      } else {
        parity = 0; // placed at odd, ready for even again
      }
    }
    // If result length is odd, need one more deletion to make it even
    if parity == 1 {
      del += 1;
    }
    del
  }
}