快读
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;
}
归并排序
void msort(int left ,int right)
{
int mid=(left+right)/2;
int pos_l=left;
int pos_r=mid+1;
int pos=left;
if(left>=right)
return;
msort(left,mid);
msort(mid+1,right);
while(pos_l<=mid && pos_r<=right)
{
if(a[pos_l] <= a[pos_r])
temp[pos++]=a[pos_l++];
else
temp[pos++]=a[pos_r++];
}
while(pos_l<=mid)
temp[pos++]=a[pos_l++];
while(pos_r<=right)
temp[pos++]=a[pos_r++];
while(left<=right)
{
a[left]=temp[left];
left++;
}
}
O2优化（吸氧）
#pragma GCC optimize(2)
标签：ch,int,代码,pos,mid,有用,right,日常,left From： https://www.cnblogs.com/LiuYT2004/p/17784730.html