/**
 Write a function that takes a string as input and returns the string reversed.

Example:
Given s = "hello", return "olleh".

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*/

/*
 Thinking:
 这个比较简单，只需要一左一右交换，知道相遇就可以了
 */

func reverseString(_ s: String) -> String {
    guard s.lengthOfBytes(using: .ascii) > 1 else {
        return s
    }
    
    var array = s.characters.map { String($0) }
    
    func swapArray(_ left: Int, _ right: Int) {
        if (left != right) {
            swap(&array[left], &array[right])
        }
    }
    
    var left = 0
    var right = array.count - 1
    while left < right {
        swapArray(left, right)
        left += 1
        right -= 1
    }
    
    return array.joined()
}

reverseString("a")
reverseString("ab")
reverseString("acddeasfaf")