Reverse All Words in a String 反轉字符串中的所有單詞

Reverse All Words in a String 反轉字符串中的所有單詞

解法1

class Solution {
    func reverseWords(_ s: String) -> String {
        if s.count <= 1 {
        return s
        }
        var result = ""
        let array = s.split(separator: " ")
        for characters in array {
            result = result + characters.reversed() + " ";
        }
        result.removeLast()
        return result;
    }
}

解法2

class Solution {
    func reverseWords(_ s: String) -> String {
        if s.count <= 1 {
        return s
        }
        let array = s.split(separator: " ")
        let result = array.map { String($0.reversed()) }
        return result.joined(separator: " ")
    }
}

解法3

上面的兩種方法都使用了Swift原生的反轉方法reversed(), 如果要求自己實現呢 ?

/// 反轉一個指定的字符串
fileprivate func _reverse(_ chars: inout [Character], _ start: inout Int, _ end: inout Int) {
    while start < end {
        _swap(&chars, start, end);
        start += 1
        end -= 1
    }
}

/// 交換字符數組中的兩個字符元素
fileprivate func _swap(_ chars: inout [Character], _ p: Int, _ r: Int) {
    (chars[p], chars[r]) = (chars[r], chars[p])
}