# 1526. Minimum Number of Increments on Subarrays to Form a Target Array

Given an array of positive integers `target` and an array `initial` of same size with all zeros.

Return the minimum number of operations to form a `target` array from `initial` if you are allowed to do the following operation:

• Choose any subarray from `initial` and increment each value by one.
The answer is guaranteed to fit within the range of a 32-bit signed integer.

Example 1:

```Input: target = [1,2,3,2,1]
Output: 3
Explanation: We need at least 3 operations to form the target array from the initial array.
[0,0,0,0,0] increment 1 from index 0 to 4 (inclusive).
[1,1,1,1,1] increment 1 from index 1 to 3 (inclusive).
[1,2,2,2,1] increment 1 at index 2.
[1,2,3,2,1] target array is formed.
```

Example 2:

```Input: target = [3,1,1,2]
Output: 4
Explanation: (initial)[0,0,0,0] -> [1,1,1,1] -> [1,1,1,2] -> [2,1,1,2] -> [3,1,1,2] (target).
```

Example 3:

```Input: target = [3,1,5,4,2]
Output: 7
Explanation: (initial)[0,0,0,0,0] -> [1,1,1,1,1] -> [2,1,1,1,1] -> [3,1,1,1,1]
-> [3,1,2,2,2] -> [3,1,3,3,2] -> [3,1,4,4,2] -> [3,1,5,4,2] (target).
```

Example 4:

```Input: target = [1,1,1,1]
Output: 1
```

Constraints:

• `1 <= target.length <= 10^5`
• `1 <= target[i] <= 10^5`

Hard

Normal