Technically, the term "random number generator" is nonsense, since numbers themselves are not random. For example, is 100 a random number? What about 25? What this term actually means is that it creates a sequence of numbers that appear randomly. This raises a more difficult question: what is a sequence of random numbers? The only correct answer: a sequence of random numbers is a sequence in which all elements are unrelated. This definition leads to the paradox that any sequence can be either random or non-random, depending on how the sequence is obtained. For example, the following string of numbers
1 2 3 4 5 6 7 8 9 0
was obtained by typing the top line of the keyboard in order, so the sequence cannot be considered randomly generated. But what if you get the same sequence when you take the numbered tennis balls out of the barrel. In this case, it is already a randomly generated sequence. This example shows that the randomness of a sequence depends on how it was obtained, not on itself.

Remember that a computer-generated sequence of numbers is deterministic: each number except the first one depends on the numbers before it. Technically, this means that only a quasi-random sequence of numbers can be generated by a computer, i.e. in fact they are not truly random. However, this is sufficient for most tasks and for simplicity such sequences will be called random. One very interesting method was developed by John von Neumann; it is often called root mean square. In this method, the previous random number is squared, and then the middle digits are extracted from the result. For example, if you are creating numbers with three digits, and the previous number was 121, then squaring it gives the result 14641. Isolating the middle three digits gives the next random number 464. The disadvantage of this method is that it has a very short repetition period, called a cycle . For this reason this method not used today. Modern methods Generating random numbers is much more difficult.

Random numbers in PHP

PHP has two groups of functions for working with random numbers. Purely externally, they can be distinguished by the mt_ prefix for all functions of one of the groups.

Deprecated features
rand function Returns an integer between zero and the value of RAND_MAX (which is 32767). Can have two optional integer parameters - if they are specified, a random number is generated from the first parameter to the second.

Echo rand(); echo rand(1,100); // Give out a random number from 1 to 100

Function srand. Specifies the sequence of random numbers produced by the rand function. Has a whole parameter - when different meanings With this parameter, rand will produce different sequences of numbers. The srand function only needs to be called once before all calls to the rand function. Usage example:

Srand(1288); // Initialize the random number generator for($i=0; $i number of elements in range = 247 - 78 + 1 = 170; (Since both boundaries include

/*Mthod 1:*/ var i = 78, j = 247, k = 170, a = , b = , c, d, e, f, l = 0;< 0) { num3 += 2147483647; } this.SeedArray = num3; this.inext = num; this.inextp = num2; return num3; }; Random.prototype.Sample = function () { return this.InternalSample() * 4.6566128752457969E-10; }; Random.prototype.GetSampleForLargeRange = function () { var num = this.InternalSample(); var flag = this.InternalSample() % 2 == 0; if (flag) { num = -num; } var num2 = num; num2 += 2147483646.0; return num2 / 4294967293.0; }; Random.prototype.Next = function (minValue, maxValue) { if (!minValue && !maxValue) return this.InternalSample(); var num = maxValue - minValue; if (num количество элементов диапазона = 247 - 78 + 1 = 170; (так как обе границы включены.

for(; i = 56) ( num = 1; ) if (++num2 >= 56) ( num2 = 1; ) var num3 = this.SeedArray - this.SeedArray;

if (num3 == 2147483647) ( num3--; ) if (num3

/*Mthod 1:*/ var i = 78, j = 247, k = 170, a = , b = , c, d, e, f, l = 0;< how_many_number; i++) { var gen_num = parseInt((Math.random() * (max-min+1)) + min); do { var is_exist = random_number.indexOf(gen_num); if (is_exist >for(; i 20) ( bool = true; ) else ( bool = false; ) ) return number; )

Using the following code, you can generate an array of random numbers without repetition within a given range.

Function genRandomNumber(how_many_number,min,max) ( // parameters // how_many_number: how many numbers you want to generate. For example it is 5. // min(inclusive) : minimum/low value of a range. it must be any positive integer but less than max. i.e 4 // max(inclusive) : maximun value of a range. it must be any positive integer. i.e 50 // return type: array var random_number = for (var i = 0; i

= 0) ( gen_num = parseInt((Math.random() * (max-min+1)) + min); ) else ( random_number.push(gen_num); is_exist = -2; ) ) while (is_exist > -1 );

) document.getElementById("box").innerHTML = random_number;

)

To get a random number, say between 1 and 6, first do:

Var value = 0.5 + (Math.random() * ((6 - 1) + 1)) var roll = Math.round(value);

return roll;

In general, the code for this using variables is:

Var value = (Min - 0.5) + (Math.random() * ((Max - Min) + 1)) var roll = Math.round(value);

return roll;

The reason to subtract 0.5 from the minimum value is that using only the minimum value will allow you to get an integer that would be greater than your maximum value. By removing 0.5 from the minimum value you are essentially preventing the maximum value from being rounded up.

Hope this helps.

Random integer between lowest and highest:

Function randomRange(l,h)( var range = (h-l); var random = Math.floor(Math.random()*range); if (random === 0)(random+=1;) return l+random; )

Not the most elegant solution.. but something fast.

Function getRandomInt(lower, upper) ( //to create an even sample distribution return Math.floor(lower + (Math.random() * (upper - lower + 1))); //to produce an uneven sample distribution // return Math.round(lower + (Math.random() * (upper - lower))); //to exclude the max value from the possible values ​​//return Math.floor(lower + (Math.random() * ( upper - lower)));< Number.MIN_SAFE_INTEGER) { throw new Error("Arguments must be safe integers."); } else if (range >To test this feature and variations of this feature, save the below HTML/JavaScript to a file and open it in a browser. The code will show a graph showing the distribution of one million function calls. The code will also record edge cases, so if the function produces a value greater than max, or less than min, you.will.know.about.it.< min) { throw new Error("max (${max}) must be >= min ($(min)."); ) else if (min === max) ( return min; ) let generated; do ( generated = crypto.getRandomValues(new Uint32Array(1)); ) while (generated > maxUnbiased); return min + (generated % possibleResultValues); console.log(randomInteger(-8, 8)); // -2 console.log(randomInteger(0, 0)); randomInteger(0, 0xFFFFFFFF)); // 944450079 console.log(randomInteger(-1, 0xFFFFFFFF)); // Error: Range of 4294967296 covering -1 to 4294967295 is > 4294967295. console.log(new Array(12). fill().map(n => randomInteger(8, 12)));

An “algorithm” for randomly selecting values ​​from an array without repeating them. More specifically, as part of my JS training, I used it to generate a classic RPG group of characters (barbarian, mage, thief, knight, priest), without repeating classes and names.

The principle is extremely simple, but it can be useful for JS beginners like me. The connection to RPG is purely symbolic - now I’m actively trying to change my profile from marketing to IT (I realized that my soul lies), and practicing in a game form is much more interesting.

1. Create a template Before generating a group of characters, you need to set a template for their generation. Actually, here it is:

Function GamePlayer(n, r, l, p) ( this.nick = n; this.role = r; this.level = l; this.portrait = p; )
In fact, this function will create characters from the variables through which it will be called. For example:

Var player1 = new GamePlayer("Power Ranger","barbarian","64","img/barbarian.jpg")
Now the player1 variable stores a level 64 Power Ranger barbarian with a specific portrait; we can display any of its parameters in the body of the page using player1.nick , player1.level , etc.

The values ​​(n, r, l, p) from GamePlayer are responsible for receiving and the order in which data is received into the function. If in the example we swap n and r, then the powerful ranger Barbarian will remain in player1, which does not quite correspond to the task.

2. Define arrays In order not to create characters ourselves, but to almost randomly generate them (as promised in the title), we need arrays from which we will take the parameters of these same characters. As already described above, we have only 4 parameters: character name, class, level and portrait.

Array for name:

Var playerNames = ["Rabbit Helpless", "Warm Dreaded Foal", "Desire Kit", "Angel Dusty", "Sweety Frozen", "Silver Heavy Wombat", "Lost Puma", "Vital Panda", "Rolling Sun" , "Steel Runny", "Young Fox", "Needless Ruthless Volunteer", "Chipmunk Cult", "Indigo Puppy"];
It would be possible to go further and generate names from 2-3 components, but the algorithm for such an improvement does not contain anything new (the same randomness), and then it would simply complicate the learning process.

Array for class:

Var playerRoles = ["barbarian", "mage", "rogue", "knight", "priest"];
Everything is just as obvious. Several strings, from which we will then select values ​​to display on the page.

Array for level:

In this particular example, I wanted all party members to be between level 60 and 70. But, since conditions may change, it was necessary to create an array from level 0 to 80, from which then select the required values. Created in a loop:

Var playerLevels = ; for (i = 0;i