Swift版全排列-Heap's Algorithm

概述Swift 全排列算法，递归版和非递归版，都有！ 参考于Wiki-Heap's algorithm 很有Swift特色，不是简单的翻译而已，废话不多说，直接上代码（Swift3+）： import Foundation/// 递归全排列func heapsAlgorithmPermutationRecursive<T: Collection>(list: T) -> [[T.Iterator

Swift 全排列算法，递归版和非递归版，都有！ 参考于Wiki-Heap's algorithm

很有Swift特色，不是简单的翻译而已，废话不多说，直接上代码（Swift3+）：

import Foundation/// 递归全排列func heapsAlgorithmPermutationRecursive<T: Collection>(List: T) -> [[T.Iterator.Element]] {    var result: [[T.Iterator.Element]] = []    var temp = Array(List)    // Heap's Algorithm recursive    func heap(n: Int) {        if n == 1 {            result.append(temp)        }else {            for i in 0..<n-1 {                heap(n: n-1)                swap(&temp[n%2 == 0 ? i : 0],&temp[n-1])            }            heap(n: n-1)        }    }    // start    heap(n: temp.count)    return result}/// 非递归全排列func heapsAlgorithmPermutationNonRecursive<T: Collection>(List: T) -> [[T.Iterator.Element]] {    var result: [[T.Iterator.Element]] = []    var temp = Array(List)    var index = [Int](repeating: 0,count: temp.count)    var i = 0    // Heap's Algorithm non-recursive    result.append(temp)    while i < temp.count {        if index[i] < i {            swap(&temp[i%2 == 0 ? 0 : index[i]],&temp[i])            result.append(temp)            index[i] += 1            i = 0        }else {            index[i] = 0            i += 1        }    }    return result}// 测试数据//let List = Array(1...7)var List = "abc".charactersvar date = NSDate()var result: [[Any]]// 递归result = heapsAlgorithmPermutationRecursive(List: List)print("递归:\ncount:\(result.count)\n耗时:\(date.timeIntervalSinceNow)")print(result)// 非递归date = NSDate()result = heapsAlgorithmPermutationNonRecursive(List: List)print(date.timeIntervalSinceNow)print("非递归:\ncount:\(result.count)\n耗时:\(date.timeIntervalSinceNow)")print(result)// 去重测试List = "abb".charactersresult = heapsAlgorithmPermutationNonRecursive(List: List)print("未去重前结果:\n\(result)")let combine = result.flatMap { (c) -> String in    let r = c as! [Character]    return r.reduce("") {a,b in        a + String(b)    }}let norepeat = Set(combine)print("去重后:\n\(norepeat)")

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