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Commit 515b1fc

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feat: add swift implementation to lcof2 problem: No.114 (doocs#3692)
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‎lcof2/剑指 Offer II 114. 外星文字典/README.md‎

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@@ -349,6 +349,78 @@ func alienOrder(words []string) string {
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}
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```
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#### Swift
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```swift
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class Solution {
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func alienOrder(_ words: [String]) -> String {
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var graph = Array(repeating: Set<Int>(), count: 26)
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var indegree = Array(repeating: 0, count: 26)
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var seen = Array(repeating: false, count: 26)
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var letterCount = 0
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for i in 0..<words.count - 1 {
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for char in words[i] {
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let index = Int(char.asciiValue! - Character("a").asciiValue!)
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if !seen[index] {
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seen[index] = true
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letterCount += 1
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}
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}
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let minLength = min(words[i].count, words[i + 1].count)
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for j in 0..<minLength {
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let char1 = words[i][words[i].index(words[i].startIndex, offsetBy: j)]
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let char2 = words[i + 1][words[i + 1].index(words[i + 1].startIndex, offsetBy: j)]
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if char1 != char2 {
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let c1 = Int(char1.asciiValue! - Character("a").asciiValue!)
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let c2 = Int(char2.asciiValue! - Character("a").asciiValue!)
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if !graph[c1].contains(c2) {
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graph[c1].insert(c2)
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indegree[c2] += 1
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}
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break
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}
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if j == minLength - 1 && words[i].count > words[i + 1].count {
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return ""
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}
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}
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}
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for char in words[words.count - 1] {
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let index = Int(char.asciiValue! - Character("a").asciiValue!)
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if !seen[index] {
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seen[index] = true
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letterCount += 1
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}
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}
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var queue = [Int]()
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for i in 0..<26 {
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if seen[i] && indegree[i] == 0 {
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queue.append(i)
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}
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}
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var order = ""
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while !queue.isEmpty {
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let u = queue.removeFirst()
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order += String(UnicodeScalar(u + Int(Character("a").asciiValue!))!)
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for v in graph[u] {
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indegree[v] -= 1
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if indegree[v] == 0 {
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queue.append(v)
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}
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}
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}
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return order.count == letterCount ? order : ""
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}
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}
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```
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<!-- tabs:end -->
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<!-- solution:end -->
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class Solution {
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func alienOrder(_ words: [String]) -> String {
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var graph = Array(repeating: Set<Int>(), count: 26)
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var indegree = Array(repeating: 0, count: 26)
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var seen = Array(repeating: false, count: 26)
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var letterCount = 0
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for i in 0..<words.count - 1 {
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for char in words[i] {
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let index = Int(char.asciiValue! - Character("a").asciiValue!)
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if !seen[index] {
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seen[index] = true
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letterCount += 1
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}
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}
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let minLength = min(words[i].count, words[i + 1].count)
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for j in 0..<minLength {
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let char1 = words[i][words[i].index(words[i].startIndex, offsetBy: j)]
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let char2 = words[i + 1][words[i + 1].index(words[i + 1].startIndex, offsetBy: j)]
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if char1 != char2 {
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let c1 = Int(char1.asciiValue! - Character("a").asciiValue!)
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let c2 = Int(char2.asciiValue! - Character("a").asciiValue!)
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if !graph[c1].contains(c2) {
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graph[c1].insert(c2)
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indegree[c2] += 1
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}
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break
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}
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if j == minLength - 1 && words[i].count > words[i + 1].count {
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return ""
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}
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}
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}
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for char in words[words.count - 1] {
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let index = Int(char.asciiValue! - Character("a").asciiValue!)
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if !seen[index] {
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seen[index] = true
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letterCount += 1
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}
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}
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var queue = [Int]()
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for i in 0..<26 {
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if seen[i] && indegree[i] == 0 {
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queue.append(i)
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}
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}
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var order = ""
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while !queue.isEmpty {
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let u = queue.removeFirst()
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order += String(UnicodeScalar(u + Int(Character("a").asciiValue!))!)
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for v in graph[u] {
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indegree[v] -= 1
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if indegree[v] == 0 {
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queue.append(v)
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}
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}
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}
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return order.count == letterCount ? order : ""
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}
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}

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