Swift-字符串排列

题目:确定某字符串的全部排列组合.

核心代码:

   func getPerms(str:String) -> [String] {
        
        var permutations:[String] = []
        
        if str.characters.count == 0 {
            permutations.append("")
            return permutations
        }
        
        let first:String = str[0]
        let index = str.index(str.startIndex, offsetBy: 1)
        let remainder:String = str.substring(from: index)
        let words:[String] = getPerms(str: remainder)
        
        for word in words {
            
            for i in 0...word.characters.count {
                let str:String = insertCharAt(word: word, mid: first, i: i)
                permutations.append(str)
            }
        }
        
        return permutations
    }
    
    func insertCharAt(word:String,mid:String,i:Int) -> String {
        let index = word.index(word.startIndex, offsetBy: i)
        let start:String = word.substring(to: index)
        let end:String = word.substring(from: index)
        let result = start + mid + end
        
        return result
    }

测试代码:

var permutations:[String] = recursion.getPerms(str: "abc")
print("FlyElephant---字符串排列:\(permutations)")

FlyElephant.png