Create Random generator with out repeating again the last one generated On swift (xcode)

Question

Hello everyone I've been trying to create a game for a couple of weeks however I'm unable to create a function that randomly plays a new function all the time without replaying the same function it just played before.

I've been using the following script to generate a random function to play.

func playgame(){   
var randomgen = arc4random % 6                   
switch(randomgen){             
case 0:          
 game1()        
break      
case 1:   
 game2()   
break  
case 2:    
 game3()  
 break  
case 3:  
 game4()  
break  
case 4:   
 game5()  
 break  
case 5:   
 game6()   
 break   
default:    
 break     
  }    

When the player presses a button the function runs again generating a random game function.
How can I generate a random game without generating the same game that has been generated befor.
For example: if game1() was generated and I press the next game button I want to generate a random game from the other 5 games available. The idea is to be able to play the six game indefinitely.

Answer 1

I would recommend to make an NSArray of all games, then randomly select one of the games from NSArray index, remove randomized game so next time it will select randomly any of remaining games in NSArray.

That's the only way to make sure it won't repeat. You could control randomizer by using seeded version, but that only gives you an option to make it repeatable.

It can be easily achieved by making NSArray category:

- (id) randomARC4Element
{
    if(self.count > 0)
    {
        return [self objectAtIndex:[self randomIntBetweenMin:0 andMax:self.count-1]];
    }

    return nil;
}

- (int)randomIntBetweenMin:(int)minValue andMax:(int)maxValue
{
    return (int)(minValue + [self randomFloat] * (maxValue - minValue));
}

- (float)randomFloat
{
    return (float) arc4random() / UINT_MAX;
}

After all games are played, you can just recreate an array.

If you want to randomize a game just making sure that only the last one won't repeat, I would recommend keeping last randomized elements, creating NSArray of all elements, remove last randomized element and randomize any of elements from such an array - that is guarantee result after only one randomize iteration.

Answer 2

Make a while loop to check for last game.

var lastGame = -1

func playGame() {

    var randomgen = 0

    repeat {
        randomgen = arc4random % 6
    } while (randomgen == lastGame)

    lastGame = randomgen

    switch randomgen {
        case 1: game1()
        case 2: game2()    
        /* ... */
        default:
    }
}  

Avoiding infinite loop scenario in some cases. But also needs improvements in case when lastGame exceeds your games number

var lastGame = -1

func playGame() {

    var randomgen = 0
    var counter = 0
    let limit = 10

    repeat {
        randomgen = arc4random % 6
        counter++
    } while (randomgen == lastGame && counter < limit)

    if counter == limit {
        randomgen = lastGame + 1
    }

    lastGame = randomgen

    switch randomgen {
        case 1: game1()
        case 2: game2()    
        /* ... */
        default:
    }
}