C++ Random Number

Question

I created a random number generator (between 100 and 1) for an Array but each time I run it it outputs the same 10 numbers between 1 and 100.

for (int x=0; x < 10; x++) {
       arr[x]=rand() % 100 + 1;

The Loop runs 10 times because the array contains 10 integers. Every time I run this though, it outputs: 42, 68, 35, 1, 70, 25, 79, 59, 63, 65.

It Outputs from this line of code

 for (int z=0; z<10;z++) {
       cout << arr[z]<<", ";
 }

Can anyone see why this is happening?

"Can anyone see why this is happening?" because you do not bother to read the documentation http://www.cplusplus.com/reference/cstdlib/rand/ — Slava, Dec 21 '17 at 20:07
I'll just leave these links here (*please* don't use `(s)rand` in new/modern code) : http://en.cppreference.com/w/cpp/numeric/random , https://channel9.msdn.com/Events/GoingNative/2013/rand-Considered-Harmful — Jesper Juhl, Dec 21 '17 at 20:10
@Slava cplusplus.com is a pretty poor quality reference. Prefer cppreference.com .. — Jesper Juhl, Dec 21 '17 at 20:11
@JesperJuhl I know but `rand()` is not a good quality function, so I think this is fine. — Slava, Dec 21 '17 at 20:15

Francis Cugler · Answer 1 · 2017-12-21T20:12:52.710

0

When using rand() it will generate the same sequence from the given input to srand(). Another words it will typically use the same generated numbers from the initial seed value. These functions are considered to be frowned upon in their use and some even want them to be marked as deprecated in favor of the modern std pseudo-random number generators library.

To generate random numbers try using the library from the <random> header instead.

You can find the documentations here: cppreference::random

edited Dec 21 '17 at 20:12

answered Dec 21 '17 at 20:08

Francis Cugler

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The first sentence is less than clear - by design, `rand` will always generate the same sequence, given a particular input to `srand`. – Oliver Charlesworth Dec 21 '17 at 20:10
@OliverCharlesworth true; I was just trying to stress on the better use of the `` library. – Francis Cugler Dec 21 '17 at 20:11

C++ Random Number

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