344. Reverse String

Problem

Tags: Two Pointers, String, Recursion

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:

• 1 <= s.length <= 10^5
• s[i] is a printable ascii character.

Code

C

// 344. Reverse String (10/26/54217)
// Runtime: 48 ms (88.76%) Memory: 12.32 MB (38.80%) 

void reverseString (char* s, int size) {
    int half = size / 2;
    int last = size - 1;
    
    for (int i = 0; i < half; i++) {
        char tmp = s[i];
        s[i] = s[last - i];
        s[last - i] = tmp;
    }
}

JS

// 344. Reverse String (4/1/53720)
// Runtime: 127 ms (39.44%) Memory: 46.52 MB (94.82%) 

/**
 * @param {character[]} s
 * @return {void} Do not return anything, modify s in-place instead.
 */
function reverseString(s) {
    for (let i = 0; i < parseInt(s.length / 2); i++) [s[i], s[s.length - 1 - i]] = [s[s.length - 1 - i], s[i]];
}

RS

// 344. Reverse String (11/12/54217)
// Runtime: 17 ms (53.48%) Memory: 5.39 MB (93.97%) 

impl Solution {
    pub fn reverse_string(s: &mut Vec<char>) {
        s.reverse();
    }
}