LeetCode - Reverse String

Reverse String - LeetCode

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문제

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

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

You may assume all the characters consist of printable ascii characters.

 

Example 1:

Input: ["h","e","l","l","o"] Output: ["o","l","l","e","h"]

Example 2:

Input: ["H","a","n","n","a","h"] Output: ["h","a","n","n","a","H"]

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class Solution {
    func reverseString(_ s: inout [Character]) {
        helper(&s, 0)
    }
    func helper(_ s: inout [Character], _ index: Int ){
        
        if  s.count/2  <= index  {
            return
        }
       
        let tmp = s[index]
        s[index] = s[s.count-index-1]
        s[s.count-index-1] = tmp
        helper(&s, index+1)
    }
}