344. Reverse String

344. Reverse String

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 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:

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

Solution:

class Solution {

    /**
     * @param String[] $s
     * @return NULL
     */
    function reverseString(&$s) {
        $l = 0;
        $r = count($s) - 1;

        while ($l < $r) {
            list($s[$l], $s[$r]) = array($s[$r], $s[$l]);
            $l++;
            $r--;
        }
    }
}

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