objective-c - 在 Objective-C 中生成随机数

Question

我主要是Java头，我想要一种方法来生成0到74之间的伪随机数。在Java中我会使用方法:

Random.nextInt(74)

我对关于种子或真正随机性的讨论不感兴趣，只是讨论如何在 Objective-C 中完成相同的任务。我搜索了谷歌，似乎有很多不同且相互矛盾的信息。

Answer 1

您应该使用 arc4random_uniform() 函数。它使用优于 rand 的算法。你甚至不需要设置种子。

#include <stdlib.h>
// ...
// ...
int r = arc4random_uniform(74);

arc4random 手册页:

NAME
     arc4random, arc4random_stir, arc4random_addrandom -- arc4 random number generator

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <stdlib.h>

     u_int32_t
     arc4random(void);

     void
     arc4random_stir(void);

     void
     arc4random_addrandom(unsigned char *dat, int datlen);

DESCRIPTION
     The arc4random() function uses the key stream generator employed by the arc4 cipher, which uses 8*8 8
     bit S-Boxes.  The S-Boxes can be in about (2**1700) states.  The arc4random() function returns pseudo-
     random numbers in the range of 0 to (2**32)-1, and therefore has twice the range of rand(3) and
     random(3).

     The arc4random_stir() function reads data from /dev/urandom and uses it to permute the S-Boxes via
     arc4random_addrandom().

     There is no need to call arc4random_stir() before using arc4random(), since arc4random() automatically
     initializes itself.

EXAMPLES
     The following produces a drop-in replacement for the traditional rand() and random() functions using
     arc4random():

           #define foo4random() (arc4random() % ((unsigned)RAND_MAX + 1))