卡常剪贴板
编译命令优化
放在代码头部，比赛不可用。
手动O2优化
#pragma GCC optimize("O2")
手动O3优化
#pragma GCC optimize("O3")
三行
#pragma GCC optimize("O2")
#pragma GCC optimize("Ofast")
#pragma GCC optimize("inline")
火车头
#pragma GCC optimize(2)
#pragma GCC optimize(3)
#pragma GCC optimize("Ofast")
#pragma GCC optimize("inline")
#pragma GCC optimize("-fgcse")
#pragma GCC optimize("-fgcse-lm")
#pragma GCC optimize("-fipa-sra")
#pragma GCC optimize("-ftree-pre")
#pragma GCC optimize("-ftree-vrp")
#pragma GCC optimize("-fpeephole2")
#pragma GCC optimize("-ffast-math")
#pragma GCC optimize("-fsched-spec")
#pragma GCC optimize("unroll-loops")
#pragma GCC optimize("-falign-jumps")
#pragma GCC optimize("-falign-loops")
#pragma GCC optimize("-falign-labels")
#pragma GCC optimize("-fdevirtualize")
#pragma GCC optimize("-fcaller-saves")
#pragma GCC optimize("-fcrossjumping")
#pragma GCC optimize("-fthread-jumps")
#pragma GCC optimize("-funroll-loops")
#pragma GCC optimize("-fwhole-program")
#pragma GCC optimize("-freorder-blocks")
#pragma GCC optimize("-fschedule-insns")
#pragma GCC optimize("inline-functions")
#pragma GCC optimize("-ftree-tail-merge")
#pragma GCC optimize("-fschedule-insns2")
#pragma GCC optimize("-fstrict-aliasing")
#pragma GCC optimize("-fstrict-overflow")
#pragma GCC optimize("-falign-functions")
#pragma GCC optimize("-fcse-skip-blocks")
#pragma GCC optimize("-fcse-follow-jumps")
#pragma GCC optimize("-fsched-interblock")
#pragma GCC optimize("-fpartial-inlining")
#pragma GCC optimize("no-stack-protector")
#pragma GCC optimize("-freorder-functions")
#pragma GCC optimize("-findirect-inlining")
#pragma GCC optimize("-fhoist-adjacent-loads")
#pragma GCC optimize("-frerun-cse-after-loop")
#pragma GCC optimize("inline-small-functions")
#pragma GCC optimize("-finline-small-functions")
#pragma GCC optimize("-ftree-switch-conversion")
#pragma GCC optimize("-foptimize-sibling-calls")
#pragma GCC optimize("-fexpensive-optimizations")
#pragma GCC optimize("-funsafe-loop-optimizations")
#pragma GCC optimize("inline-functions-called-once")
#pragma GCC optimize("-fdelete-null-pointer-checks")
FastIO
普通快读
namespace FastIO
{
char c;
bool sign;
template<class T>
inline void read(T &x)
{
x=0;
sign=false;
for(c=getchar();c<'0'||c>'9';c=getchar())
if(c=='-')
sign=true;
for(;c>='0'&&c<='9';c=getchar())
x=(x<<1)+(x<<3)+(c&15);
if(sign) x=~x+1;
return;
}
}
using FastIO::read;
不建议手写快输，可能比 printf 都慢。
快读
1号。
namespace FastIO
{
const int _SIZE = (1 << 21) + 1;
char ibuf[_SIZE],*iS,*iT;
inline char getc()
{
if(iS==iT)
iS=ibuf,iT=iS+fread(ibuf,1,_SIZE,stdin);
return (iS == iT ? EOF : *iS++);
}
template <class T>
inline void read(T &x)
{
x=0;
register char c;
register bool sign=false;
for (c=getc();c<'0' || c>'9';c=getc())
if (c=='-') sign=true;
for (;c>='0' && c<='9';c=getc())
x=(x<<1)+(x<<3)+(c&15);
if(sign) x=~x+1;
}
}
using FastIO::getc;
using FastIO::read;
2号。
namespace FastIO
{
const int _SIZE = (1 << 21) + 1;
char ibuf[_SIZE],*iS,*iT;
char obuf[_SIZE],*oS=obuf,*oT=obuf+_SIZE-1;
inline char getc()
{
if(iS==iT)
iS=ibuf,iT=iS+fread(ibuf,1,_SIZE,stdin);
return (iS == iT ? EOF : *iS++);
}
template <class T>
inline void read(T &x)
{
x=0;
register char c;
register bool sign=false;
for (c=getc();c<'0' || c>'9';c=getc())
if (c=='-') sign=true;
for (;c>='0' && c<='9';c=getc())
x=(x<<1)+(x<<3)+(c&15);
if(sign) x=~x+1;
}
inline void flush() { fwrite(obuf,1,oS-obuf,stdout); oS=obuf; }
inline void putc(register char x) { *oS++=x; if(oS==oT) flush(); }
template <class T>
inline void write(T x) {
static char qu[50];
register int qr;
if (!x) return putc('0');
if (x<0) putc('-'),x=~x+1;
for(qr=1;x;qr++,x/=10) qu[qr]=x%10+'0';
for(qr--;qr>=1;qr--) putc(qu[qr]);
}
struct Flusher_
{
~Flusher_() { flush(); }
}io_flusher_;
}
using FastIO::getc;
using FastIO::putc;
using FastIO::read;
using FastIO::write;
#define enter FastIO::putc('\n')
注意不可以与其他读入方式混用。
其他
适当使用关键字
register
inline
#define
参考文献：
