思路:
使用朴素字符串搜索,依次扫描整个字符串
/// 查找所有的子字符串所在位置
/// - Parameter string: 给定的模式P
func findAllIndex(_ string:String) -> [NSRange]{
var ranges:[NSRange] = []
if string.elementsEqual(""){
return ranges
}
let zero = self.startIndex
let target = Array(string)
let total = Array(self)
let lenght = string.count
var startPoint = 0
while total.count >= startPoint + string.count{
if total[startPoint] == target[0]{
let startIndex = self.index(zero, offsetBy: startPoint)
let endIndex = self.index(startIndex, offsetBy: lenght)
let child = self[startIndex..<endIndex]
if child.elementsEqual(string){
ranges.append(NSRange.init(location: startPoint, length: lenght))
startPoint += lenght
}else{
startPoint += 1
}
}else{
startPoint += 1
}
}
return ranges
}
使用KMP算法实现:
/// KMP字符串查询
/// - Parameter p: 查询的模式
func kmpFindAllIndex(_ p:String) -> [NSRange]{
var ranges:[NSRange] = []
let n = self.count
let m = p.count
let π = computePrefix(p)
var q = 0
for i in 0..<n{
while q > 0 && !p.getCharacter(q).elementsEqual(self.getCharacter(i)){
q = π[q]
}
if p.getCharacter(q).elementsEqual(self.getCharacter(i)){
q += 1
}
if q == m{
ranges.append(NSRange.init(location: i, length: m))
q = π[q]
}
}
return ranges
}
/// 计算KMP对应的前缀函数π数组
/// - Parameter p: 模式P
func computePrefix(_ p:String) -> [Int]{
let m = p.count
var π:[Int] = [Int](repeatElement(0, count: m + 1))
π[0] = 0
var k = 0
for q in 1..<m{
while k > 0 && !p.getCharacter(k).elementsEqual(p.getCharacter(q)){
k = π[k]
}
if p.getCharacter(k).elementsEqual(p.getCharacter(q)){
k += 1
}
π[q] = k
}
return π
}
/// 获取单个字符
/// - Parameter index: <#index description#>
func getCharacter(_ index:Int) -> String{
return getChildsString(index, 1)
}
/// 获取特定位置,长度 字符串
/// - Parameters:
/// - start: 开始位置
/// - length: 长度
func getChildsString(_ start:Int,_ length:Int) -> String{
let startIndex = self.index(self.startIndex, offsetBy: start)
let endIndex = self.index(startIndex, offsetBy: length)
return String(self[startIndex..<endIndex])
}
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