这段49字符的C程序可运行10^10100890年

这段 49 字符的C程序可运行 10^10100890 年，是不是很有趣？来看看吧

a[1<<20];n;main (){while(!(n>>20))n=++a[n]?0:n+1;}    /*  Quite slow program in 49 characters  Andrew Belt    Assuming an int is 32 bits, this program halts in around 2^(32*2^20) loops.  This will take at least 10^10100890 years.    The array `a` is essentially a large integer spread across consecutive ints.  This program simply increments the integer and halts when it overflows.  I believe this approach gives the most loops possible with a state variable of 4*2^20 bytes (4 MiB).    Future improvements might include allocating memory on the heap instead, or opening and closing emacs in each iteration of the loop.  */