卡常技巧

来个代码

#include<bits/stdc++.h> 
#define O3 __attribute__((optimize("-O3"))) 
#define O2 __attribute__((optimize("-O2"))) 
#define setIO(s) freopen(s".in","r",stdin) , freopen(s".out","w",stdout)    
#define maxn 100002 
#define rint register int 
#define rg register  
#define inf 100000000 
#define isrt(x) (!(ch[f[x]][0]==x||ch[f[x]][1]==x)) 
#define get(x) (ch[f[x]][1]==x) 
#define lson ch[x][0] 
#define rson ch[x][1]  
using namespace std; 
inline int read(){
    rint x=0,f=1;char ch=getchar();
    while (ch<'0' || ch>'9'){if (ch=='-')f=-1;ch=getchar();}
    while ('0'<=ch && ch<='9')x=(x<<1)+(x<<3)+(ch^48),ch=getchar();
    return x*f;
}
int n,Q;  
multiset<int>S[maxn];    
int ch[maxn][2],f[maxn],rev[maxn],sta[maxn],minv[maxn],mintot[maxn],minson[maxn],val[maxn];         
O2 inline void mark(int x) 
{
    if(!x) return; 
    swap(lson,rson),rev[x]^=1;  
} 
O2 inline void pushup(int x)
{   
    if(!x) return; 
    minv[x]=mintot[x]=val[x],minson[x]=inf;  
    minv[x]=min(minv[x],min(minv[lson],minv[rson])); 
    minson[x]=min(min(minson[lson],minson[rson]),*S[x].begin()); 
    mintot[x]=min(minv[x], minson[x]);          
}
O2 inline void pushdown(int x)
{
    if(!x||!rev[x]) return; 
    mark(lson),mark(rson),rev[x]^=1;   
}
O2 inline void rotate(int x)
{
    int old=f[x],fold=f[old],which=get(x); 
    if(!isrt(old)) ch[fold][ch[fold][1]==old]=x;      
    ch[old][which]=ch[x][which^1],f[ch[old][which]]=old;  
    ch[x][which^1]=old,f[old]=x,f[x]=fold; 
    pushup(old),pushup(x); 
}
O2 inline void splay(int x)
{
    int v=0,u=x,fa; 
    for(sta[++v]=u;!isrt(u);u=f[u]) sta[++v]=f[u];   
    while(v) pushdown(sta[v--]); 
    for(u=f[u];(fa=f[x])!=u;rotate(x)) 
        if(f[fa]!=u) 
            rotate(get(x)==get(fa)?fa:x);         
}
O2 inline void Access(int x)
{
    int t=0; 
    while(x) 
    {  
        splay(x); 
        if(rson) S[x].insert(mintot[rson]);                                    
        if(t) S[x].erase(S[x].lower_bound(mintot[t]));    
        rson=t,t=x,x=f[x];  
    }
}
O2 inline void makert(int x) 
{
    Access(x),splay(x),mark(x);  
} 
O2 inline void link(int x,int y) 
{
    makert(x), f[x]=y, S[y].insert(mintot[x]);    
}
int edges,hd[maxn],to[maxn],nex[maxn]; 
void addedge(int u,int v) 
{
    if(!u)return; 
    nex[++edges]=hd[u],hd[u]=edges,to[edges]=v;      
} 
O2 void dfs(int u) 
{  
    for(int i=hd[u];i;i=nex[i]) 
    {
        int v=to[i]; 
        dfs(v), S[u].insert(mintot[v]); 
        pushup(u);       
    }
    pushup(u); 
}
O2 int main()
{ 
    rg int i; 
    int root=0; 
    //         setIO("input"); 
    n=read(),Q=read(); 
    mintot[0]=minv[0]=minson[0]=val[0]=inf;     
    for(i=0;i<=n;++i) S[i].insert(inf);                                 
    for(i=1;i<=n;++i) 
    {    
        int a; 
        a=read(), val[i]=read(), f[i]=a;      
        addedge(a, i);      
        if(!a) root=i;                     
    }          
    dfs(root); 
    makert(root);    
    while(Q--)
    {
        char opt[3];  
        int x,y; 
        scanf("%s",opt); 
        if(opt[0]=='V') 
        {
            x=read(), y = read();     
            Access(x), splay(x), val[x]=y, pushup(x); 
        }
        if(opt[0]=='E') 
        { 
            root = read(); 
            makert(root); 
        }
        if(opt[0]=='Q') 
        { 
            x = read(); 
            Access(x), splay(x);      
            printf("%d\n",min(val[x], *S[x].begin())); 
        }
    }
    return 0; 
}

　　

注意几点：

1. bzoj 交题一定加读入优化/输出优化 

2. LCT 的操作都非常慢，能不用就不用 

3. 加 register/O2/O3 

4. inline 好像用处不大 

标签：ch,技巧,int,void,maxn,卡常,O2,define
来源： https://www.cnblogs.com/guangheli/p/11255788.html