atoll函数搞不定，于是找了另一个办法，记下备忘

以下代码来自http://p2p.wrox.com/c-programming/16319-string-long-long-without-using-atoll.html

#include <stdio.h>
#include <string.h>
long long my_atoll(char *);
int main()
{
  char buffer[256];
  long long value;
  long long value2;
  strcpy(buffer, "1234567890123456");
  sscanf(buffer, "%lld", &value);
  printf("nn");
  printf("   Value (from sscanf)    = %lldn", value);
  value2 = my_atoll(buffer);
  printf("   Value (from my_atoll)  = %lldn", value2);
  printf("nn");
  return 0;
}



long long my_atoll(char *instr)
{
  long long retval;
  int i;

  retval = 0;
  for (; *instr; instr++) {
    retval = 10*retval + (*instr - '0');
  }
  return retval;
}