004.快读快写

为什么需要快读快写？

1. 极少题目会卡常数时间
2. 偷懒

常用 IO

• 默认cin/cout

• 优化cin/cout

  cin.tie(0)->sync_with_stdio(0)

• scanf/printf

• getchar/putchar

• fread

---

谨记用'\n'代替endl，懂的都懂orz

旧版read(),write()

#include<bits/stdc++.h>
using namespace std;//read()
inline int read(){int x=0,f=1;char ch=getchar();while(ch<'0'||ch>'9'){if(ch=='-')f*=-1;ch=getchar();}while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}return x*f;
}//write()
inline void write(int x)
{if(x<0)putchar('-'),x=-x;if(x>9)write(x/10);putchar(x%10+'0');return;
}int main(){int T=read();while(T--){int n=read(),m=read();write(n+m);putchar('\n');}
}

---

优化

一、不止 int

#include<bits/stdc++.h>
using namespace std;//read(x)
template<typename type>
inline void read(type &x){x=0,bool f=0;char ch=getchar();while(ch<'0'||ch>'9'){if(ch=='-')f=1;ch=getchar();}while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}f?x=-x:0;
}//write(x)
template<typename type>
inline void write(type x)
{if(x<0)putchar('-'),x=-x;if(x>9)write(x/10);putchar(x%10+'0');return;
}int main(){long long T,m,n;read(T);while(T--){read(m),read(n);write(m+n);}
}

除了字符串均可读写

二、进一步优化read(x)

char buf[1<<20],*p1=buf,*p2=buf;
#define nc() (p1==p2 && (p2=(p1=buf)+fread(buf,1,1<<20,stdin),p1==p2)?EOF:*p1++)
template<typename type>
inline void read(type &x){x=0;bool f(0);char ch=nc();while(ch<'0'||ch>'9')f=ch=='-',ch=nc();while(ch>='0'&&ch<='9')x=x*10+ch-'0',ch=nc();f?x=-x:0;
}

• 优点：更快！
• 缺点：对本地调试不友好，但对文件输入输出、OJ判题没有影响

ps: 如果你需要本地调试，可以使用宏定义或者配置你的编译器，最安全的方法是使用文件输入输出

当然 : 优化一已经非常够用了

三、进一步优化write(x)

使用stack而不是递归

template<typename type>
inline void write(type x){x<0?x=-x,putchar('-'):0;static short stk[50],top(0);do stk[++top]=x%10,x/=10;while(x);while(top)putchar(stk[top--]+'0');
}

我们可以进一步偷懒添加功能

template<typename type>inline void wr1(type x){wr(x),putchar(' ');}
template<typename type>inline void wr2(type x){wr(x),putchar('\n');}

功能很简单，一目了然

四、增添字符串读写

inline void readline(char *s){char ch=nc();int i(0);while(ch=='\n'||ch=='\r')ch=nc();while(ch!='\n'&&ch!='\r'&&ch!=EOF)s[i++]=ch,ch=nc();s[i]='\0';
}
inline void write(const char*s){while(*s)putchar(*s++);
}
inline void writeline(const char*s){write(s);putchar('\n');
}

五、封装

namespace IO{char buf[1<<20],*p1=buf,*p2=buf;#define nc() (p1==p2 && (p2=(p1=buf)+fread(buf,1,1<<20,stdin),p1==p2)?EOF:*p1++)template<typename type>inline void read(type&x){x=0;bool f(0);char ch=nc();while(ch<'0'||ch>'9')f=ch=='-',ch=nc();while(ch>='0'&&ch<='9')x=x*10+ch-'0',ch=nc();f?x=-x:0;}template<typename type>inline void write(type x){x<0?x=-x,putchar('-'):0;static short stk[50],top(0);do stk[++top]=x%10,x/=10;while(x);while(top)putchar(stk[top--]+'0');}template<typename type>inline void wr1(type x){wr(x),putchar(' ');}template<typename type>inline void wr2(type x){wr(x),putchar('\n');}inline void readline(char *s){char ch=nc();int i(0);while(ch=='\n'||ch=='\r')ch=nc();while(ch!='\n'&&ch!='\r'&&ch!=EOF)s[i++]=ch,ch=nc();s[i]='\0';}inline void write(const char*s){while(*s)putchar(*s++);}inline void writeline(const char*s){write(s),putchar('\n');}}using namespace IO;

产物(已压行)

简易版

便于本地调试

namespace IO{template<typename type>inline void read(type &x){x=0,bool f=0;char ch=getchar();while(ch<'0'||ch>'9'){if(ch=='-')f=1;ch=getchar();}while(ch>='0'&&ch<='9'){x=x*10+ch-'0';h=getchar();}f?x=-x:0;}template<typename type>inline void write(type x){x<0?x=-x,putchar('-'):0;static short stk[50],top(0);do stk[++top]=x%10,x/=10;while(x);while(top)putchar(stk[top--]+'0');}template<typename type>inline void wr1(type x){wr(x),putchar(' ');}template<typename type>inline void wr2(type x){wr(x),putchar('\n');}inline void readline(char *s){char ch=nc();int i(0);while(ch=='\n'||ch=='\r')ch=nc();while(ch!='\n'&&ch!='\r'&&ch!=EOF)s[i++]=ch,ch=nc();s[i]='\0';}inline void write(const char*s){while(*s)putchar(*s++);}inline void writeline(const char*s){write(s),putchar('\n');}
}using namespace IO;

优化版

添加了输入缓冲

建议文件读写

namespace IO{char buf[1<<20],*p1=buf,*p2=buf;#define nc() (p1==p2 && (p2=(p1=buf)+fread(buf,1,1<<20,stdin),p1==p2)?EOF:*p1++)template<typename type>inline void read(type&x){x=0;bool f(0);char ch=nc();while(ch<'0'||ch>'9')f=ch=='-',ch=nc();while(ch>='0'&&ch<='9')x=x*10+ch-'0',ch=nc();f?x=-x:0;}template<typename type>inline void write(type x){x<0?x=-x,putchar('-'):0;static short stk[50],top(0);do stk[++top]=x%10,x/=10;while(x);while(top)putchar(stk[top--]+'0');}template<typename type>inline void wr1(type x){wr(x),putchar(' ');}template<typename type>inline void wr2(type x){wr(x),putchar('\n');}inline void readline(char *s){char ch=nc();int i(0);while(ch=='\n'||ch=='\r')ch=nc();while(ch!='\n'&&ch!='\r'&&ch!=EOF)s[i++]=ch,ch=nc();s[i]='\0';}inline void write(const char*s){while(*s)putchar(*s++);}inline void writeline(const char*s){write(s),putchar('\n');}
}using namespace Fast::IO;

更极端

进一步添加输出缓存

可以但没必要

namespace IO{char inbuf[1<<20],outbuf[1<<20],*pin=inbuf,*pout=outbuf;
#define gc() (pin==inbuf+(1<<20)?fread(inbuf,1,1<<20,stdin),pin=inbuf,*pin++:*pin++)
#define pc(ch) (pout==outbuf+(1<<20)?fwrite(outbuf,1,1<<20,stdout),pout=outbuf,*pout++=ch:*pout++=ch)
struct AutoFlush{~AutoFlush(){fwrite(outbuf,1,pout-outbuf,stdout);}}auto_flush;
template<typename T>void read(T&x){x=0;bool f=0;char ch=gc();while(ch<'0'||ch>'9')f=ch=='-',ch=gc();while(ch>='0'&&ch<='9')x=x*10+ch-'0',ch=gc();if(f)x=-x;}
template<typename T>void write(T x){if(x<0)x=-x,pc('-');static char stk[50];int top=0;do stk[++top]=x%10+'0',x/=10;while(x);while(top)pc(stk[top--]);}
template<typename T>void write1(T x){write(x);pc(' ');}
template<typename T>void write2(T x){write(x);pc('\n');}
void write(const char*s){while(*s)pc(*s++);}
void writeln(const char*s){write(s);pc('\n');}
void readline(char*s){char ch=gc();while(ch=='\n'||ch=='\r')ch=gc();while(ch!='\n'&&ch!='\r'&&ch!=EOF)*s++=ch,ch=gc();*s='\0';}
}using namespace IO;

手动O2优化

#pragma GCC optimize(2)

贴个Solution.cpp

#include<bits/stdc++.h>
using namespace std;
#pragma GCC optimize(2)
namespace IO{char buf[1<<20],*p1=buf,*p2=buf;
#define nc() (p1==p2 && (p2=(p1=buf)+fread(buf,1,1<<20,stdin),p1==p2)?EOF:*p1++)
template<typename type>inline void read(type&x){x=0;bool f(0);char ch=nc();while(ch<'0'||ch>'9')f=ch=='-',ch=nc();while(ch>='0'&&ch<='9')x=x*10+ch-'0',ch=nc();f?x=-x:0;}template<typename type>inline void write(type x){x<0?x=-x,putchar('-'):0;static short stk[50],top(0);do stk[++top]=x%10,x/=10;while(x);while(top)putchar(stk[top--]+'0');}template<typename type>inline void wr1(type x){wr(x),putchar(' ');}template<typename type>inline void wr2(type x){wr(x),putchar('\n');}inline void readline(char *s){char ch=nc();int i(0);while(ch=='\n'||ch=='\r')ch=nc();while(ch!='\n'&&ch!='\r'&&ch!=EOF)s[i++]=ch,ch=nc();s[i]='\0';}inline void write(const char*s){while(*s)putchar(*s++);}inline void writeline(const char*s){write(s),putchar('\n');}}using namespace IO;
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
const int MOD=1000000007;
const int inf=0x3f3f3f3f;
const ll INF=0x3f3f3f3f3f3f3f3fll;
const int MAXN=100005;void solve(){
}
int main(){int T;read(T);while(T--){solve();}
}

结语

只是辅助工具，锦上添花

感谢观看