CODEWITHSUNDEEP
c++random
rajat
rajat

Reputation: 3553

Random number between 1 to 10 using C++

This code is supposed to generate random number between 1 to 10, but it returns 1 every time. 

int random_integer;
int lowest=1, highest=10;
int range=(highest-lowest)+1;
random_integer = lowest + int(range*rand()/(RAND_MAX + 1.0));
cout << random_integer << endl;

What's wrong in the code?

Upvotes: 4

Views: 84183

Answers (6)

birubisht
birubisht

Reputation: 908

I agree with all the solution provided above .
now to get a different sequence every time you run your program you can use srand() function it will provide a seed to rand() function as follows:- 

srand(time(NULL))  
random_integer = lowest + rand() % range

Upvotes: 2

SteveL
SteveL

Reputation: 3389

This two are always part of my programs

float randf(float lo, float hi) {
    float random = ((float) rand()) / (float) RAND_MAX;
    float diff = hi - lo;
    float r = random * diff;
    return lo + r;
}
int randi(int lo, int hi)
{
    int n = hi - lo + 1;
    int i = rand() % n;
    if (i < 0) i = -i;
    return lo + i;
}

Upvotes: 1

Sebastian Mach
Sebastian Mach

Reputation: 39089

You seem to assume that rand() returns a value between 0 and 1.

This is not correct, it return value between 0 and RAND_MAX.

Upvotes: 0

Fred Foo
Fred Foo

Reputation: 363527

range * rand() / (RAND_MAX + 1.0)

does not do what you think. Introduce some parens:

range * (rand() / (RAND_MAX + 1.0))

(Note that this method gives skewed distributions, though.)

Upvotes: 5

Luchian Grigore
Luchian Grigore

Reputation: 258568

You're subject to overflow here - range*rand().

Just use what regular folks use: rand() % 10 + 1.

Upvotes: 7

Anton Guryanov
Anton Guryanov

Reputation: 12457

If you want a random integer between lowest and highest, you'd better write

random_integer = lowest + rand() % range

Upvotes: 11

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