这个你在哪里看到的？rand()在很多系统上最大只返回三万多，%100000000有什么意义？
而且rand()函数在很多系统上实现都有低字节随机度不够的问题。man rand明确说了：
       In Numerical Recipes in C: The Art of Scientific Computing (William H.
       Press,  Brian  P.  Flannery, Saul A. Teukolsky, William T. Vetterling;
       New York: Cambridge University Press, 1992 (2nd  ed.,  p.  277)),  the
       following comments are made:
              "If you want to generate a random integer between 1 and 10, you
              should always do it by using high-order bits, as in

                     j=1+(int) (10.0*rand()/(RAND_MAX+1.0));

              and never by anything resembling

                     j=1+(rand() % 10);

              (which uses lower-order bits)."

【 在 yanzg (油炸鬼~新家~项王) 的大作中提到: 】
: 居然发现了
: rand() % 100000000
: 看来我可以放心用了。
: ...................
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FROM 128.12.181.*