remove resursive in C/C++

Interesting. On my machine, If I use gcc zombie.c (or g++ zombie.cc) to compile, and run it will got a segment fault.

if using "gcc -O2 zombie.c", it will be OK and get correct answer.

I guess this is because the recursive function call exceeds the stack limit , and for the O2 option the compiler have done the optimization.

remove the recursive will be OK, and C/C++ version cost time about 5.3 seconds.