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| import Foundation
class For42Solution {
//翻转字符串
func reverseWord(_ s: String) -> String {
var strs = Array(s)
//第一次整体翻转
reverse(&strs, 0, s.count-1)
//第二次单个翻转
var start = 0
var end = 0
while end < strs.count {
if strs[end] == " " {
reverse(&strs, start, end-1)
end += 1
start = end
}
end += 1
}
reverse(&strs, start, end-1)
return String(strs)
}
//左旋转字符串 abcdefg->cdefgab 从第N个开始
func leftRotateString(_ s: String,_ n: Int) -> String {
if n > s.count || s == "" {
return ""
}
var strs = Array(s)
//翻转前面一段
reverse(&strs, 0, n-1)
//翻转后面一段
reverse(&strs, n, strs.count-1)
//全部翻转
reverse(&strs, 0, strs.count-1)
return String(strs)
}
func reverse(_ strs: inout [Character],_ start1: Int,_ end1: Int) {
var start = start1
var end = end1
while start < end {
let temp = strs[start]
strs[start] = strs[end]
strs[end] = temp
start += 1
end -= 1
}
}
}
|
