How to generate different random numbers in a loop in C

Question

Is it possible to generate different random number  every time loop runs  For example  i have   for  int t 0 t lt 10 t          int random x      srand   time NULL         random x   rand     100      cout lt  lt   nRandom X     lt  lt random x       But the problem is  it generates same random number everytime  Is it possible to generate different random numbers everytime loop runs   IS there any possibility to reset random number initiallization as well

User · Answer

Don t know men  I found the best way for me after testing different ways like 10 minutes     Change the numbers in code to get big or small random number        int x  srand   time NULL     x   rand     1000   rand     10000   cout lt  lt x

User · Answer

Do not use rand    use new C  11 facilities  e g  std  mt19937  std  uniform int distribution  etc   instead   You can use code like this  live here on Ideone     include  lt iostream gt   include  lt random gt  using namespace std   int main            Random seed     random device rd          Initialize Mersenne Twister pseudo-random number generator     mt19937 gen rd             Generate pseudo-random numbers        uniformly distributed in range  1  100      uniform int distribution lt  gt  dis 1  100           Generate ten pseudo-random numbers     for  int i   0  i  lt  10  i                  int randomX   dis gen           cout  lt  lt    nRandom X      lt  lt  randomX              P S   Consider watching this video from Going Native 2013 conference for more details about rand  -related problems      rand   Considered Harmful

User · Answer

Every iteration you are resetting the sequence of pseudorandom numbers because you are calling srand with the same seed  since the call to time is so frequent   Either use a different seed  or call srand once before you enter the loop

User · Answer

Stop seeding the generator every time  Pull the srand call out of the loop

User · Answer

I had this same problem for days  Keeping srand   out of the loop is a    Also  dont assign rand     100 to any variable  Simply cout rand     100 in the loop  Try this       srand  time NULL         int t 0 t lt 10 t              cout  lt  lt  rand     100  lt  lt  endl

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this code is written in Turbo C    For Visual Studio  code is in comment    int a 10  ct 0 x 10 y 10       x y can be any value  but within the range of                                 array declared randomize                      there is no need to use this Visual Studio for int i 0 i lt 10 i        a i  random 10             use a i  rand   10 for Visual Studio   cout lt  lt   n n   do     ct 0      for i 0 i lt x i            for int j 0 j lt y j                if a i   a j  amp  amp i  j                  a j  random 10        use a i  rand   10 for Visual Studio                           else                 ct                                   while   ct   x y       Well I m not a pro in C    but learnt it in school  I am using this algo for past 1 year to store different random values in a 1D array  but this will also work in 2D array after some changes  Any suggestions about the code are welcome

User · Answer

Move the srand call to the start of the program  As you have it now  the time might be the same between two consecutive calls  so the random number generator will start again at the same spot

User · Answer

Try moving the seed srand outside the loop like so   srand   time NULL     for  int t 0 t lt 10 t          int random x      random x   rand     100      cout lt  lt    nRandom X     lt  lt random x       As Mark Ransom says in the comment  moving the seed outside the loop will only help if the loop is not residing in a function you are calling several times

User · Answer

The way the function rand   works is that every time you call it  it generates a random number  In your code  you ve called it once and stored it into the variable random x  To get your desired random numbers instead of storing it into a variable  just call the function like this   for  int t 0 t lt 10 t          cout  lt  lt    nRandom X      lt  lt  rand     100

User · Answer

You are getting the same random number each time  because you are setting a seed inside the loop  Even though you re using time    it only changes once per second  so if your loop completes in a second  which it likely will   you ll get the same seed value each time  and the same initial random number   Move the srand   call outside the loop  and call it only once  at the start of your app  and you should get random  random  numbers

User · Answer

The time function probably returns the same value during each iteration of the loop   Try initializing the random seed before the loop

User · Answer

Don t use srand inside the loop  use it only once  e g  at the start of main    And srand   is exactly how you reset this

User · Answer

You need to extract the initilization of time   out of the for loop   Here is an example that will output in the windows console expected  ahah  random number    include  lt iostream gt   include  lt windows h gt   include  time h  int main int argc  char argv          srand   time NULL         for  int t   0  t  lt  10  t                  int random x           random x   rand     100          std  cout  lt  lt    nRandom X      lt  lt  random x  lt  lt  std  endl            Sleep 50000       return 0

[c++] How to generate different random numbers in a loop in C++?

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