# Question

Formatted question description: https://leetcode.ca/all/344.html

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 with O(1) extra memory.

Example 1:

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


Example 2:

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


Constraints:

# Algorithm

Go from both ends to the middle while swapping characters on both sides.

# Code

• 
public class Reverse_String {

class Solution {
public void reverseString(char[] s) {

int l = 0;
int r = s.length - 1;

while (l < r) {
char tmp = s[l];
s[l] = s[r];
s[r] = tmp;
l++;
r--;
}
}
}

class Solution_cheat {
public String reverseString(String input) {

StringBuilder s = new StringBuilder(input);
s.reverse();

return s.toString();
}
}
}

############

class Solution {
public void reverseString(char[] s) {
for (int i = 0, j = s.length - 1; i < j; ++i, --j) {
char t = s[i];
s[i] = s[j];
s[j] = t;
}
}
}

• // OJ: https://leetcode.com/problems/reverse-string/
// Time: O(N)
// Space: O(1)
class Solution {
public:
void reverseString(vector<char>& s) {
int i = 0, j = s.size() - 1;
while (i < j) swap(s[i++], s[j--]);
}
};

• class Solution:
def reverseString(self, s: List[str]) -> None:
"""
Do not return anything, modify s in-place instead.
"""
s[:] = s[::-1]

############

class Solution(object):
def reverseString(self, s):
"""
:type s: str
:rtype: str
"""
return s[::-1]


• func reverseString(s []byte) {
for i, j := 0, len(s)-1; i < j; i, j = i+1, j-1 {
s[i], s[j] = s[j], s[i]
}
}

• /**
* @param {character[]} s
* @return {void} Do not return anything, modify s in-place instead.
*/
var reverseString = function (s) {
for (let i = 0, j = s.length - 1; i < j; ++i, --j) {
[s[i], s[j]] = [s[j], s[i]];
}
};


• impl Solution {
pub fn reverse_string(s: &mut Vec<char>) {
let n = s.len();
let mut l = 0;
let mut r = n - 1;
while l < r {
s.swap(l, r);
l += 1;
r -= 1;
}
}
}