LeetCode link:[344. Reverse String](https://leetcode.com/problems/reverse-string),

[344. 反转字符串](https://leetcode.cn/problems/reverse-string)

[中文题解](#中文题解)

LeetCode link:[344. Reverse String](https://leetcode.com/problems/reverse-string), difficulty:**Easy**.

Write a function that reverses a string. The input string is given as an array of characters`s`.

You must do this by modifying the input array[in-place](https://en.wikipedia.org/wiki/In-place_algorithm) with`O(1)` extra memory.

Difficulty:**Easy**

**Input**:`s = ["h","e","l","l","o"]`

**Output**:`["o","l","l","e","h"]`

**Input**:`s = ["H","a","n","n","a","h"]`

**Output**:`["h","a","n","n","a","H"]`

-`s[i]` is a[printable ascii character](https://en.wikipedia.org/wiki/ASCII#Printable_characters).

<details>

<summary>Hint 1</summary>

The entire logic for reversing a string is based on using the opposite directional two-pointer approach!

</details>

[中文题解](#中文题解)

1. This problem can be solved in one line of code using the built-in`sort()` method of the programming language. If this question is asked in an interview, the questioner should be testing how to do it without the built-in method.

2. Use**two pointers** with**opposite directions**, initially one pointer points to the index`0` and the other pointer points to the index`s.length - 1`.

3. Traverse the elements of the array, and the loop condition is`while (left < right)`. In the loop body,`left += 1`,`right -= 1`.

4. In the loop body, swap the two values.

5. The above is the template for`two pointers` in`opposite directions`.

1. Use two pointers with**opposite directions**, initially one pointer points to the index`0` and the other pointer points to the index`s.length - 1`.

left=0

right= s.length-1

2. Traverse the elements of the array, and the loop condition is`while (left < right)`. In the loop body,`left += 1`,`right -= 1`.

left=0

right= s.length-1

3. In the loop body, swap the two values.

left=0

right= s.length-1

* Time:`O(n)`.

* Space:`O(1)`.

classSolution {

publicvoidreverseString(char[]s) {

classSolution:

defreverseString(self,s: List[str]) ->None:

classSolution {

public:

varreverseString=function (s) {

let left=0

{

funcreverseString(s []byte) {

defreverse_string(s)

left=0

力扣链接：[344. 反转字符串](https://leetcode.cn/problems/reverse-string) ，难度：**简单**。

编写一个函数，其作用是将输入的字符串反转过来。输入字符串以字符数组`s` 的形式给出。

不要给另外的数组分配额外的空间，你必须**原地****修改输入数组**、使用`O(1)` 的额外空间解决这一问题。

**输入**:`s = ["h","e","l","l","o"]`

**输出**:`["o","l","l","e","h"]`

1. 这种问题用编程语言内置的`sort()`方法可以一行代码解决。如果面试中出这种题目，出题人考察的应该是不用内置方法如何做。

2. 用**方向相对**的两个指针，最初时一个指针指向下标`0`，另一个指针指向下标`s.length - 1`。

3. 遍历数组元素，循环条件为`while (left < right)`。在循环体内，`left += 1`,`right -= 1`。

4. 在循环体内，交换数组中两个下标对应的值。

5. 以上为`方向相对`的**双指针**的模板。

1. 用**方向相对的两个指针**，最初时一个指针指向下标`0`，另一个指针指向下标`s.length - 1`。

left=0

right= s.length-1

2. 遍历数组元素，循环条件为`while (left < right)`。在循环体内，`left += 1`,`right -= 1`。

left=0

right= s.length-1

while left< right# 1

left+=1# 2

right-=1# 3

3. 在循环体内，交换数组中两个下标对应的值。

left=0

right= s.length-1

while left< right

s[left], s[right]= s[right], s[left]# 1

left+=1

right-=1

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