Merge pull request #1542 from Chaigidel/fixio

## 完整带调试版

关闭调试开关时使用 `fread()` , `fwrite()` ，退出时自动析构执行 `fwrite()` 。

开启调试开关时使用 `getchar()` , `putchar()` ，便于调试。

若要开启文件读写时，请在所有读写之前加入 `freopen()` 。

```cpp

#define DEBUG 1  //调试开关

namespace IO {

#define isdigit(x) x >= '0' && x <= '9'

const int MAXSIZE = 1 << 20;

// #define DEBUG 1  //调试开关

struct IO {

#define MAXSIZE (1 << 20)

#define isdigit(x) (x >= '0' && x <= '9')

  char buf[MAXSIZE], *p1, *p2;

  char pbuf[MAXSIZE], *pp;

#if DEBUG

#else

  IO() : p1(buf), p2(buf), pp(pbuf) {}

  ~IO() { fwrite(pbuf, 1, pp - pbuf, stdout); }

#endif

  inline char gc() {

#if DEBUG  //调试，可显示字符

    return getchar();

#endif

  static char buf[MAXSIZE], *p1 = buf + MAXSIZE, *p2 = buf + MAXSIZE;

    if (p1 == p2) p2 = (p1 = buf) + fread(buf, 1, MAXSIZE, stdin);

    return p1 == p2 ? -1 : *p1++;

  }

    register char ch = gc();

    for (; !isdigit(ch); ch = gc())

      if (ch == '-') sign = 1;

  for (; isdigit(ch); ch = gc()) x = x * 10 + ch - '0';

    for (; isdigit(ch); ch = gc()) x = x * 10 + (ch - '0');

    if (ch == '.')

    for (ch = gc(); isdigit(ch); ch = gc()) tmp /= 10.0, x += tmp * (ch - 48);

      for (ch = gc(); isdigit(ch); ch = gc())

        tmp /= 10.0, x += tmp * (ch - '0');

    if (sign) x = -x;

  }

  inline void read(char *s) {

      ;

  }

  inline void push(const char &c) {

  char pbuf[MAXSIZE], *pp = pbuf;

#if DEBUG  //调试，可显示字符

    putchar(c);

#else

    if (pp - pbuf == MAXSIZE) fwrite(pbuf, 1, MAXSIZE, stdout), pp = pbuf;

    *pp++ = c;

#endif

  }

  template <class T>

  inline void write(T x) {

    if (x < 0) x = -x, push('-');  // 负数输出

    static T sta[35];

    T top = 0;

    do {

      sta[top++] = x % 10, x /= 10;

    } while (x);

#if DEBUG  //调试，可显示字符

  while (top) putchar(sta[--top] + '0');

  return;

#endif

    while (top) push(sta[--top] + '0');

  }

  template <class T>

  inline void write(T x, char lastChar) {

  write(x), putchar(lastChar);  //打印末尾字符 ex.'\n'

    write(x), push(lastChar);

  }

}  // namespace IO

using namespace IO;

} io;

```

## 参考