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Merge pull request #944 from ShrinkLynn/master
[ShrinkLynn] 0028 add swift version
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@ -894,7 +894,58 @@ var strStr = function (haystack, needle) {
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};
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```
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Swift 版本
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> 前缀表统一减一
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```swift
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func strStr(_ haystack: String, _ needle: String) -> Int {
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let s = Array(haystack), p = Array(needle)
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guard p.count != 0 else { return 0 }
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// 2 pointer
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var j = -1
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var next = [Int](repeating: -1, count: needle.count)
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// KMP
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getNext(&next, needle: p)
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for i in 0 ..< s.count {
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while j >= 0 && s[i] != p[j + 1] {
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//不匹配之后寻找之前匹配的位置
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j = next[j]
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}
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if s[i] == p[j + 1] {
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//匹配,双指针同时后移
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j += 1
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}
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if j == (p.count - 1) {
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//出现匹配字符串
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return i - p.count + 1
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}
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}
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return -1
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}
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//前缀表统一减一
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func getNext(_ next: inout [Int], needle: [Character]) {
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var j: Int = -1
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next[0] = j
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// i 从 1 开始
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for i in 1 ..< needle.count {
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while j >= 0 && needle[i] != needle[j + 1] {
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j = next[j]
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}
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if needle[i] == needle[j + 1] {
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j += 1;
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}
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next[i] = j
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}
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print(next)
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}
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```
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-----------------------
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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>
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