位图算法（空间换时间）

#include <stdio.h>
#include <Windows.h>
void init(char *data, int len)
{
  unsigned int n = len * 8;
  char* p = NULL;
  for (unsigned int i = 0; i < n; i++)
  {
    if (i % 3 == 0)
    {
      p = data + i / 8;
      *p = *p | (1 << i % 8);
    }
  }
}
bool check(char* data, int len, int value)
{
  char* p = data + value / 8;
  bool ret = *p & (1 << (value % 8));
  return ret;
}
int main(void)
{
  unsigned int n = 4000000000;
  int len = n / 8 + 1;
  char* data = (char*)malloc(len);
  memset(data, 0, len);
  init(data, len);
  while (1)
  {
    printf("请输入要监测的数：[输入-1退出]");
    int value;
    scanf_s("%d", &value);
    if (value == -1)
    {
      break;
    }
    if (check(data, len, value))
    {
      printf("%d在数据集合中\n", value);
    }
    else
    {
      printf("%d不在数据集合中\n", value);
    }
  }
  system("pause");
  return 0;
}