# 1332. Remove Palindromic Subsequences

## LeetCode [1332. Remove Palindromic Subsequences](https://github.com/txfs19260817/LeetCode-Go/blob/master/solutions/title/README.md)

### Description

You are given a string `s` consisting **only** of letters `'a'` and `'b'`. In a single step you can remove one **palindromic subsequence** from `s`.

Return *the **minimum** number of steps to make the given string empty*.

A string is a **subsequence** of a given string if it is generated by deleting some characters of a given string without changing its order. Note that a subsequence does **not** necessarily need to be contiguous.

A string is called **palindrome** if is one that reads the same backward as well as forward.

**Example 1:**

```
Input: s = "ababa"
Output: 1
Explanation: s is already a palindrome, so its entirety can be removed in a single step.
```

**Example 2:**

```
Input: s = "abb"
Output: 2
Explanation: "abb" -> "bb" -> "". 
Remove palindromic subsequence "a" then "bb".
```

**Constraints:**

* `1 <= s.length <= 1000`
* `s[i]` is either `'a'` or `'b'`.

### Tags

String

### Solution

* Return 0 if it's an empty string;
* Return 1 if it's a palindrome string;
* Return 2, because what we need to remove are **substrings**. We can remove all `a` then all `b`.

### Complexity

* Time complexity: $$O(n)$$
* Space complexity: $$O(n)$$

### Code

```go
func removePalindromeSub(s string) int {
	if len(s) == 0 {
		return 0
	}
	for l, r := 0, len(s)-1; l < r; l, r = l+1, r-1 {
		if s[l] != s[r] {
			return 2
		}
	}
	return 1
}
```