Minimum Operations to Make Array Non Decreasing

You are given an integer array nums of length n.

In one operation, you may choose any subarray nums[l..r] and increase each element in that subarray by x, where x is any positive integer.

Return the minimum possible sum of the values of x across all operations required to make the array non-decreasing.

An array is non-decreasing if nums[i] <= nums[i + 1] for all 0 <= i < n - 1.

Example 1:

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

Output: 2

Explanation:

One optimal set of operations:

• Choose subarray [2..3] and add x = 1 resulting in [3, 3, 3, 2]

• Choose subarray [3..3] and add x = 1 resulting in [3, 3, 3, 3]

The array becomes non-decreasing, and the total sum of chosen x values is 1 + 1 = 2.

Example 2:

Input: nums = [5,1,2,3]

Output: 4

Explanation:

One optimal set of operations:

• Choose subarray [1..3] and add x = 4 resulting in [5, 5, 6, 7]

The array becomes non-decreasing, and the total sum of chosen x values is 4.

Constraints:

• 1 <= n == nums.length <= 105

• 1 <= nums[i] <= 109

class Solution {

    public long minOperations(int[] nums) {

        long sum = 0;

        for (int i = 0; i < nums.length-1; i++) {

            if (nums[i] > nums[i+1]) {

                long diff = nums[i] - nums[i+1];

                for (int l = i+1; l < nums.length; l++) {

                    nums[l] += diff;

                }

                sum += diff;

            }

        }

        return sum;

    }

}

Test cases:

Case 1:

nums=[3,3,2,1]

Expected: 2

Actual: 2

Case 2:

nums=[5,1,2,3]

Expected: 4

Actual: 4