Leetcode 0344. Reverse String

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"]　

Easy

Description

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 characters.

Solution

class Solution {
  /**
   * Two Pointer's
   * Analysis
   * - Time Complexity: BigO(N)
   * - Space Complexity: BigO(1)
   */
  public void reverseString(char[] s) {
    int j = s.length - 1;
    for (int i = 0; i < s.length/2; i++) {
      char temp = s[i];
      s[i] = s[j];
      s[j] = temp;
      j--;
    }
  }
}