Question

How to create permutations of a string without repetition in Swift

Answer 1

import Foundation

func stringPermutations(_ str: String) -> [String] {
    var result = [String]()
    var chars = Array(str)
    
    stringPermutationsCreate(&chars, 0, &result)
    
    return result
}

private func stringPermutationsCreate(_ chars: inout [Character], _ index: Int, _ result: inout [String]) {
    if index == chars.count {
        result.append(String(chars))
        return
    }
    
    for i in index..<chars.count {
        chars.swapAt(index, i)
        stringPermutationsCreate(&chars, index + 1, &result)
        chars.swapAt(index, i) // backtrack
    }
}

let s = "abc"

let permutations = stringPermutations(s)

print(permutations)



/*
run:

["abc", "acb", "bac", "bca", "cba", "cab"]

*/

 

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