CODEWITHSUNDEEP
javascript
wong1
wong1

Reputation: 59

Lottery number generator with no duplicates

I'm in the early stages of learning JavaScript and I had thought of making a lottery number generator for practice. This is what I have so far (z is for the total lottery balls, and y for the number of digits to be generated):

function generateRandomNumbers(z,y){
            var resultArray = [];
            var output = "";

            if(isNaN(z) || isNaN(y)){
                return "You have entered an invalid value";
            }else{
            for(x=0; x<y; x++){
                var result = Math.ceil(Math.random()*z);
                resultArray.push(result);

                output += resultArray[x]+ "\n";
                }
            }   
            return output;
        }

The problem is, this doesn't prevent duplicates from occurring. What could be a good way to ensure that the array's content doesn't contain any duplicates? I apologize if this has already been asked before.

Upvotes: 2

Views: 1529

Answers (3)

fuyushimoya
fuyushimoya

Reputation: 9813

As its lottery, the possible numbers are contiguous. You can create a list that holds all possible number, then use .splice to take one from them each time, until you take enough numbers:

function generateRandomNumbers(z,y){
    // You can't take more, or you can set y = z;
    if (y > z) {
      return [];
    }
  
    var numbers = [];
    var result = [];
    var i;
    // Create list.
    for (i = 1; i <= z; ++i) {
        numbers.push(i);
    }

    var random;
    // Take a random number from list each time.
    for (i = 0; i < y; ++i) {
        random = Math.floor(Math.random() * z);
      
        // Put the randomly take number into result.
        result.push(numbers.splice(random, 1)[0]);
      
        // As we take one number from the list, remember to decrease the possible range by 1.
        --z;
    }
    return result;
    // If you want  a string form
    // return result.join('\n');
}

console.log(generateRandomNumbers(49, 6))

Upvotes: 2

Hacketo
Hacketo

Reputation: 4997

You can test if the number that was just generated is already in resultArray.

If so, then just try to loop again for this number

for(var x = 0 ; x < y ; x++){
    var result = Math.ceil(Math.random()*z);

    if (resultArray.indexOf(result) > -1){
        x--;
    }
    else{
        resultArray.push(result);
    }
}

return resultArray.join("\n");

Also you have to check for y <= z because you can't generate more unique numbers than the range [0 - [z.

Upvotes: 0

xcoder
xcoder

Reputation: 1436

I suggest using jQuery...

var uniqueNum= [];
$.each(num, function(i, el){
   if($.inArray(el, uniqueNum) == -1) 
         uniqueNum.push(el);
});

nice and easy =]

Upvotes: 0

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