c++快读快写

c++快读快写

1. cin换成in,cout换成out,cerr换为err
2. 输出换行:out<<endln err<<endln
3. 输出清空缓存(flush): out<<flush err<<flush (不手动清理则在程序结束时自动清理)
4. get line:string s;in.getline(s);或char s[10000];getline(s);
5. 支持int128,支持while(in>>x)和while(in.getline(s))
6. 输出设置小数精度out<<precision(6)(默认:$6$)
7. 若小数位不足是否补$0$out<<force(false)(默认:$false$)
8. 小于精度的部分是否四舍五入(否则截断)out<<round(true)(默认:$true$)
9. 整数长度不足时添加前导$0$out<<lead(1)(默认:$1$)

1. 默认缓存区大小为in out 各1MB($2^{20}$字节) err缓存为$1$字节

2. 修改缓存大小: 例如将out的缓存设置为$2^{10}$字节,将$179$行的out(stdout)改为out(stdout,1<<10)

3. 程序异常退出($RE$)可能导致out的缓存没有清空(没被输出),将缓存区设为$1$字节可避免这一情况,但会导致效率下降.(若希望提高err的效率或避免out缓存没被清空,可修改它们的缓存大小)

4. getchar(),putchar(c),puts(s)现在应该使用in.getc(),out.putc(c),out<<s否则可能导致输出错乱

5. 文件输入输出可以使用freopen重定向stdio也可以创建新的对象,例:

   struct Out out(stdout),err(stderr,1);
   struct In in(stdin);
      
   struct Out fout0("out0.out"); //创建文件输出,输出到"out0.out"缓存为2^20字节
   struct Out fout1("out1.out",1024);//创建文件输出,输出到"out1.out"缓存为1024字节
   struct In fin0("in0.in");//创建文件输入,从"in0.in"读入,缓存2^20字节
   struct In fin1("in1.in",1024);//创建文件输入,从"in1.in"读入,缓存1024字节
      
   string x;
   in>>x;//标准输入
   out<<x;//标准输出
   err<<x;//标准错误输出
      
   fin0>>x;//从"in0.in"输入
   fout0<<x;//输出到"out0.out"
   

#include <bits/stdc++.h>
using namespace std;
struct Out
{
private:
    FILE*file;
    char*buf,*p1,*pend;
    int precision=6;
    bool force=false;
    bool round=true;
    int wight=0;
public:
    explicit Out(FILE*file,int size=1<<20):file(file),buf(new char[size]),p1(buf),pend(buf+size){}
    explicit Out(const string&file,int size=1<<20):Out(fopen(file.c_str(),"w"),size){}
    Out(const Out&)=delete;
    Out&operator=(const Out&)=delete;
    Out(Out&&)=delete;
    Out&operator=(Out&&)=delete;
    void setPrecision(int x){precision=x;}
    void setForce(bool x){force=x;}
    void setRound(bool x){round=x;}
    void setLead(int x){wight=x;}
    ~Out(){flush();delete[] buf;}
    void flush(){fwrite(buf,1,p1-buf,file),p1=buf;}
    void putc(char c){*p1++=c;if (p1==pend)flush();}
#define retp(x) template<class T> typename enable_if<x,Out>::type
#define lmt(x) x<T>::value
    retp(lmt(is_unsigned)&&lmt(is_integral))&operator<<(T x)
    {
        static char s[50];
        int len=0;
        do
        {
            s[len++]=x%10+'0';
            x/=10;
        } while (x||len<wight);
        while (len--)putc(s[len]);
        return *this;
    }
    retp(lmt(is_signed)&&lmt(is_integral))&operator<<(T x)
    {
        make_unsigned_t<T> y=x;
        if (x<0)putc('-'),y=-y;
        *this<<y;
        return *this;
    }
    retp(lmt(is_floating_point))&operator<<(T x)
    {
        if (x!=x)putc('N'),putc('a'),putc('N');
        else if (x==numeric_limits<T>::infinity())putc('I'),putc('n'),putc('f');
        else if (x==-numeric_limits<T>::infinity())putc('-'),putc('I'),putc('n'),putc('f');
        else
        {
            if (x<0)putc('-'),x=-x;
            if (round)x+=0.5*pow(0.1,precision);
            auto t=static_cast<intmax_t>(x);
            *this<<t;
            x-=t;
            x*=pow(10,precision);
            t=static_cast<intmax_t>(x);
            while (t%10==0&&t&&!force)t/=10;
            if (t||force)putc('.'),*this<<t;
        }
        return *this;
    }
#undef retp
#undef lmt
    Out&operator<<(const char*s){while (*s)putc(*s++);return *this;}
    Out&operator<<(const string&s){for (auto c:s)putc(c);return *this;}
    Out&operator<<(const char&c){putc(c);return *this;}
    Out&operator<<(const function<void(Out&)>&f){f(*this);return *this;}
};
const function<void(Out&)> endln=[](Out&o){o.putc('\n');};
const function<void(Out&)> flush=[](Out&o){o.flush();};
function<void(Out&)> precision(int n){return [n](Out&o){o.setPrecision(n);};}
function<void(Out&)> force(bool b){return [b](Out&o){o.setForce(b);};}
function<void(Out&)> round(bool b){return [b](Out&o){o.setRound(b);};}
function<void(Out&)> lead(int n){return [n](Out&o){o.setLead(n);};}
struct In
{
private:
    FILE*file;
    char*buf,*p1,*pend;
    bool eof;
    bool rd=true;
    void read(){p1=buf;pend=buf+fread(buf,1,pend-buf,file);eof=pend==p1;}
public:
    explicit In(FILE*file,int size=1<<20):file(file),buf(new char[size]),p1(buf+size),pend(buf+size),eof(false){}
    explicit In(const string&file,int size=1<<20):In(fopen(file.c_str(),"r"),size){}
    In(const In&)=delete;
    In&operator=(const In&)=delete;
    In(In&&)=delete;
    In&operator=(In&&)=delete;
    ~In(){delete[] buf;}
    char getc(){if (p1==pend)read();return eof?(char)-1:*p1++;}
    char peek(){if (p1==pend)read();return eof?(char)-1:*p1;}
    explicit operator bool ()const{return rd;}
#define retp(x) template<class T> typename enable_if<x,In>::type
#define lmt(x) x<T>::value
    retp(lmt(is_unsigned)&&lmt(is_integral))&operator>>(T&x)
    {
        rd=false;
        x=0;
        char c;
        while (!isdigit(c=getc())&&c!=-1);
        for (;isdigit(c);c=getc())x=x*10+c-'0',rd=true;
        return *this;
    }
    retp(lmt(is_signed)&&lmt(is_integral))&operator>>(T&x)
    {
        rd=false;
        x=0;
        char c;
        while (!isdigit(c=getc())&&c!='-'&&c!=-1);
        bool neg=false;
        if (c=='-')neg=true,c=getc();
        for (;isdigit(c);c=getc())x=x*10+(neg?'0'-c:c-'0'),rd=true;
        return *this;
    }
    retp(lmt(is_floating_point))&operator>>(T&x)
    {
        rd=false;
        x=0;
        char c;
        while (!isdigit(c=getc())&&c!='-'&&c!=-1);
        bool neg=false;
        if (c=='-')neg=true,c=getc();
        for (;isdigit(c);c=getc())x=x*10+(neg?'0'-c:c-'0'),rd=true;
        if (c=='.')
        {
            c=getc();
            T y=0;
            int cnt=0;
            for (;isdigit(c);c=getc())y=y*10+(neg?'0'-c:c-'0'),cnt++;
            x+=y*pow(0.1,cnt);
        }
        return *this;
    }
#undef retp
#undef lmt
    In&operator>>(char *s)
    {
        rd=false;
        while (isspace(*s=getc())&&*s!=-1);
        while (!isspace(*++s=getc())&&*s!=-1)rd=true;
        *s=0;
        return *this;
    }
    In&operator>>(string&s)
    {
        rd=false;
        s.clear();
        char c;
        while (isspace(c=getc())&&c!=-1);
        for (;!isspace(c)&&c!=-1;c=getc())s+=c,rd=true;
        return *this;
    }
    In&operator>>(char&c)
    {
        while (isspace(c=getc())&&c!=-1){}
        rd=c!=-1;
        return *this;
    }
    In&getline(char*s)
    {
        while ((*s=getc())=='\n'&&*s!=-1){}
        while ((*++s=getc())!='\n'&&*s!=-1)rd=true;
        return *s=0,*this;
    }
    In&getline(string&s)
    {
        s.clear();
        char c;
        while ((c=getc())=='\n'&&c!=-1){}
        for (;c!='\n'&&c!=-1;c=getc())s+=c,rd=true;
        return *this;
    }
};
struct Out out(stdout),err(stderr,1);
struct In in(stdin);