Any random number in a range that allows a computer to be random in a C + + language

Source: Internet
Author: User

This is part of the question I met in the written test, which is recorded. For example, output any random number in [1,3].

1#include <iostream>2#include <cstdlib>3#include <cstdio>4#include <ctime>5 6 7 intMain ()8 {9 Srand ((unsigned) time (NULL));Ten  One     intval =0; A      for(inti =0; I < -; i++) -     { -val = (rand ()%3) +1; theStd::cout << i +1<<" "<< Val <<Std::endl; -     } -     return 0; -}

What does line nineth mean in the code?

In the C language, the rand () function can be used to generate random numbers, but this is not the true meaning of the random number, is a pseudo-random number, is based on a number, we can call it a seed, as a reference to a recursive formula derived from a coefficient, when the series of a large number of times, it is normal to publish, This is equivalent to generating a random number, but this is not a true random number, when the computer is properly booted, the value of this seed is fixed, unless you destroy the system, in order to change the value of this seed, C provides the Srand () function, its prototype is void Srand (int a)

1) First give Srand () a seed, it is a unsigned int type, its value range from 0~65535;

2) then call Rand (), which returns a random number (between 0 and 32767) based on the seed value provided to Srand ()

inductive : To obtain a random integer between [a, b], use (rand ()% (b-a)) + A or (rand () * (b-a))/Rand_max + A

REF:

http://blog.csdn.net/qin_zhangyongheng/article/details/8033936

Any random number in a range that allows a computer to be random in a C + + language

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