Segmentation fault (core dumped)

这个 该死的错误：搞了一天。

http://www.cprogramming.com/debugging/segfaults.html

五种可能：

dereferencing NULL,

dereferencing an uninitialized pointer,

dereferencing a pointer that has been freed (or deleted, in C++) or that has gone out of scope (in the case of arrays declared in functions), and

writing off the end of an array

a recursive function that uses all of the stack space.