普通：
ios::sync_with_stdio(0);
cin.tie(0);
inline int read(){
int x=0,f=1;
char ch=getchar();
while(!isdigit(ch)){if(ch=='-')f=-1;ch=getchar();}
while(isdigit(ch)){x=(x<<3)+(x<<1)+(ch^48);ch=getchar();}
return x*f;
}
inline void write(int x){
if(x<0){
putchar('-');
x=-x;
}
if(x>9)
write(x/10);
putchar(x%10+'0');
}
进阶：
namespace FastIO {
char buf[1 << 10], buf2[1 << 21], a[21], *p1 = buf, *p2 = buf, hh = '\n';
int p, p3 = -1;
void read() {}
void print() {}
inline int getc() {
return p1 == p2 && (p2 = (p1 = buf) + fread(buf, 1, 1 << 10, stdin), p1 == p2) ? EOF : *p1++;
// 缓冲区以空 p2赋成读入后的地址，p1赋成头地址，尝试读入 是否相等 结束读入 返回p1,p1向后挪
}
inline void flush() {
fwrite(buf2, 1, p3 + 1, stdout), p3 = -1;
}
inline void read(int &x) {
register int f = 1;
x = 0;
char ch = getc();
while (!isdigit(ch)) {
if (ch == '-') f = -1;
ch = getc();
}
while (isdigit(ch)) {
x = (x << 1) + (x << 3) + (ch ^ '0');
ch = getc();
}
x = x * f;
}
inline void print(int x) {
if (p3 > 1 << 21) flush();
if (x < 0) buf2[++p3] = '-', x = -x;
do { a[++p] = x % 10 + 48; } while (x /= 10);
do { buf2[++p3] = a[p];} while (--p);
buf2[++p3] = hh;
}
}
#define read FastIO::read
#define print FastIO::print
.
.
.
FastIO :: flush();//main()
头文件：
#pragma GCC diagnostic error "-std=c++11"
#pragma GCC target("avx")
#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")