344. Reverse String

\344. Reverse String

Easy

Write a function that reverses a string. The input string is given as an array of characters char[].

Do not allocate extra space for another array, you must do this by modifying the input array in-place with O(1) extra memory.

You may assume all the characters consist of printable ascii characters.

Example 1:

1 2	Input: ["h","e","l","l","o"] Output: ["o","l","l","e","h"]

Example 2:

1 2	Input: ["H","a","n","n","a","h"] Output: ["h","a","n","n","a","H"]

two pointer (one while loop)

class Solution:
    def reverseString(self, s: List[str]) -> None:
        """
        Do not return anything, modify s in-place instead.
        """
        if not s: return
        lo = 0
        hi = len(s)-1
        while(lo <= hi):
            s[lo], s[hi] = s[hi], s[lo]
            lo += 1
            hi -= 1

one for loop

class Solution:
    def reverseString(self, s: List[str]) -> None:
        """
        Do not return anything, modify s in-place instead.
        """
        if not s: return
        for i in range(len(s) // 2):
          	s[i], s[-i-1] = s[-i-1], s[i]