LeetCode-in-Java

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:

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

Solution

public class Solution {
    public void reverseString(char[] s) {
        int left = 0;
        int right = s.length - 1;
        while (left < right) {
            char tmp = s[left];
            s[left++] = s[right];
            s[right--] = tmp;
        }
    }
}

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