Member Avatar for .:Pudge:.

What is the greatest possible range of rand()? I want to make it that of a long signed integer, but my program crashes. Is there another way to get that range?

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Short answer: the maximum value that rand() can return is implementation-defined (it is at least 32767). To get a "long" or full 64-bit signed range, do not try to stretch rand() — use the C++11 <random> facilities instead (RAND_MAX, <random> reference: https://en.cppreference.com/w/cpp/numeric/random).

was right that RAND_MAX varies; 's suggestion to multiply or combine rand() outputs can increase range but commonly introduces bias and overflow and still only produces as many bits as rand() supplies. Prefer a 64-bit engine such as std::mt19937_64 with std::uniform_int_distribution for an unbiased full-range integer generator:

#include <random>
#include <cstdint>
#include <limits>

std::random_device rd;
std::mt19937_64 gen(rd());
std::uniform_int_distribution<int64_t> dist(
    std::numeric_limits<int64_t>::min(),
    std::numeric_limits<int64_t>::max()
);

int64_t value = dist(gen); // full signed 64-bit range

If the program crashed after you tried to "make it that of a long signed integer," check these common issues: confirm the tree/search/insert functions accept the wider type (use int64_t or long long consistently), ensure no uninitialized variables are read (the posted snippet declares int j; — make sure j is initialized or only used as an out-parameter), avoid naive arithmetic on rand() results (overflow), and seed/construct your generator once rather than per-call. Use tools like a debugger, AddressSanitizer/Valgrind, or logging to see the exact failing operation.

If you need unique values, track inserts (e.g., unordered_set) or handle collisions explicitly — but beware that requesting many unique values from a small range will be slow or impossible. For more on engines and distributions see std::mt19937_64 and std::uniform_int_distribution (https://en.cppreference.com/w/cpp/numeric/random/mersenne_twister_engine, https://en.cppreference.com/w/cpp/numeric/random/uniform_int_distribution).

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Member Avatar for thelamb

The max of rand() is system-dependent.

Show us what you are doing, there may be a different reason for your program crash.

Member Avatar for .:Pudge:.

I just need to generate 'n' random numbers from within as large a range as the system will allow. Here is my code:

void randomNumGen(node *root, int n){
    int randNumResult=0;
    int j;
    for (int i=0; i<n; i++){
        randNumResult=rand ();
        if(!(search(randNumResult, root, j))
             insert(randNumResult, root);
    }
}
Member Avatar for thelamb

There is a macro 'RAND_MAX' which gives you the maximum, but it is not defined in _all_ systems.

Member Avatar for Tellalca

You may product two random numbers generated by the rand() function to get a bigger random number. That's just an example. You can create your own random number generator function.

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