README_EN.md

344. Reverse String

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Description

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

 

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:

• 1 <= s.length <= 105
• s[i] is a printable ascii character.

 

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

Solutions

Python3

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

Java

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;
        }
    }
}

C++

class Solution {
public:
    void reverseString(vector<char>& s) {
        for (int i = 0, j = s.size() - 1; i < j; ++i, --j)
            swap(s[i], s[j]);
    }
};

Go

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]
	}
}

JavaScript

/**
 * @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]];
    }
};

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