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# 1529. Bulb Switcher IV

<https://leetcode.com/problems/bulb-switcher-iv>

## Description

There is a room with `n` bulbs, numbered from `0` to `n - 1`, arranged in a row from left to right. Initially, all the bulbs are **turned off**.

Your task is to obtain the configuration represented by `target` where `target[i]` is `'1'` if the `ith` bulb is turned on and is `'0'` if it is turned off.

You have a switch to flip the state of the bulb, a flip operation is defined as follows:

* Choose **any** bulb (index `i`) of your current configuration.
* Flip each bulb from index `i` to index `n - 1`.

When any bulb is flipped it means that if it is `'0'` it changes to `'1'` and if it is `'1'` it changes to `'0'`.

Return *the **minimum** number of flips required to form* `target`.

**Example 1:**

```
**Input:** target = "10111"
**Output:** 3
**Explanation:** Initial configuration "00000".
flip from the third bulb:  "00000" -> "00111"
flip from the first bulb:  "00111" -> "11000"
flip from the second bulb:  "11000" -> "10111"
We need at least 3 flip operations to form target.
```

**Example 2:**

```
**Input:** target = "101"
**Output:** 3
**Explanation:** "000" -> "111" -> "100" -> "101".
```

**Example 3:**

```
**Input:** target = "00000"
**Output:** 0
```

**Example 4:**

```
**Input:** target = "001011101"
**Output:** 5
```

**Constraints:**

* `1 <= target.length <= 105`
* `target[i]` is either `'0'` or `'1'`.

## ac

```java
```