3834 Minimum Operations To Convert All Elements To Zero

Minimum Operations to Convert All Elements to Zero

You are given an array nums of size n, consisting of non-negative integers. Your task is to apply some (possibly zero) operations on the array so that all elements become 0.

In one operation, you can select a subarray [i, j] (where 0 <= i <= j < n) and set all occurrences of the minimum non-negative integer in that subarray to 0.

Return the minimum number of operations required to make all elements in the array 0.

 

Example 1:

Input: nums = [0,2]

Output: 1

Explanation:

Select the subarray [1,1] (which is [2]), where the minimum non-negative integer is 2. Setting all occurrences of 2 to 0 results in [0,0].
Thus, the minimum number of operations required is 1.

Example 2:

Input: nums = [3,1,2,1]

Output: 3

Explanation:

Select subarray [1,3] (which is [1,2,1]), where the minimum non-negative integer is 1. Setting all occurrences of 1 to 0 results in [3,0,2,0].
Select subarray [2,2] (which is [2]), where the minimum non-negative integer is 2. Setting all occurrences of 2 to 0 results in [3,0,0,0].
Select subarray [0,0] (which is [3]), where the minimum non-negative integer is 3. Setting all occurrences of 3 to 0 results in [0,0,0,0].
Thus, the minimum number of operations required is 3.

Example 3:

Input: nums = [1,2,1,2,1,2]

Output: 4

Explanation:

Select subarray [0,5] (which is [1,2,1,2,1,2]), where the minimum non-negative integer is 1. Setting all occurrences of 1 to 0 results in [0,2,0,2,0,2].
Select subarray [1,1] (which is [2]), where the minimum non-negative integer is 2. Setting all occurrences of 2 to 0 results in [0,0,0,2,0,2].
Select subarray [3,3] (which is [2]), where the minimum non-negative integer is 2. Setting all occurrences of 2 to 0 results in [0,0,0,0,0,2].
Select subarray [5,5] (which is [2]), where the minimum non-negative integer is 2. Setting all occurrences of 2 to 0 results in [0,0,0,0,0,0].
Thus, the minimum number of operations required is 4.

 

Constraints:

1 <= n == nums.length <= 105
0 <= nums[i] <= 105

impl Solution {
    pub fn min_operations(nums: Vec<i32>) -> i32 {
        let mut s: Vec<i32> = Vec::new();
        let mut res: i32 = 0;
        for a in nums {
            while s.last().map_or(false, |&x| x > a) {
                s.pop();
            }
            if a == 0 { continue; }
            if s.last().map_or(true, |&x| x < a) {
                res += 1;
                s.push(a);
            }
        }
        res
    }
}