import Foundation
func generateUniqueRandomString(total: Int) -> String {
let chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"
var result = ""
var usedChars = Set<Character>()
while result.count < total {
let randomIndex = Int.random(in: 0..<chars.count)
let randomChar = chars[chars.index(chars.startIndex, offsetBy: randomIndex)]
if !usedChars.contains(randomChar) {
result.append(randomChar)
usedChars.insert(randomChar)
}
}
return result
}
print(generateUniqueRandomString(total: 15))
/*
run:
RYAh8vTI1qBGbx9
*/