Merge pull request #944 from ShrinkLynn/master

[ShrinkLynn] 0028 add swift version
This commit is contained in:
程序员Carl
2021-12-19 11:35:39 +08:00
committed by GitHub

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@ -894,7 +894,58 @@ var strStr = function (haystack, needle) {
};
```
Swift 版本
> 前缀表统一减一
```swift
func strStr(_ haystack: String, _ needle: String) -> Int {
let s = Array(haystack), p = Array(needle)
guard p.count != 0 else { return 0 }
// 2 pointer
var j = -1
var next = [Int](repeating: -1, count: needle.count)
// KMP
getNext(&next, needle: p)
for i in 0 ..< s.count {
while j >= 0 && s[i] != p[j + 1] {
//不匹配之后寻找之前匹配的位置
j = next[j]
}
if s[i] == p[j + 1] {
//匹配,双指针同时后移
j += 1
}
if j == (p.count - 1) {
//出现匹配字符串
return i - p.count + 1
}
}
return -1
}
//前缀表统一减一
func getNext(_ next: inout [Int], needle: [Character]) {
var j: Int = -1
next[0] = j
// i 从 1 开始
for i in 1 ..< needle.count {
while j >= 0 && needle[i] != needle[j + 1] {
j = next[j]
}
if needle[i] == needle[j + 1] {
j += 1;
}
next[i] = j
}
print(next)
}
```
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<div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>