【题解】Luogu CF817F MEX Queries

原题传送门

817,我突然想到了某8位质数

这题珂以说是珂朵莉树的模板

三个操作都肥肠简单,前两个区间赋值,第三个区间0变1,1变0

每次输出从头开始扫描就行(我忘了珂朵莉树的性质,竟然还动态维护最左边0的位置)

#include <bits/stdc++.h>
#define getchar nc
#define ll long long
#define IT set<node>::iterator
using namespace std;
inline char nc(){
static char buf[100000],*p1=buf,*p2=buf;
return p1==p2&&(p2=(p1=buf)+fread(buf,1,100000,stdin),p1==p2)?EOF:*p1++;
}
inline ll read()
{
register ll x=0,f=1;register char ch=getchar();
while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
while(ch>='0'&&ch<='9')x=(x<<3)+(x<<1)+ch-'0',ch=getchar();
return x*f;
}
inline void write(register ll x)
{
if(!x)putchar('0');if(x<0)x=-x,putchar('-');
static int sta[25];register int tot=0;
while(x)sta[tot++]=x%10,x/=10;
while(tot)putchar(sta[--tot]+48);
}
inline ll Min(register ll a,register ll b)
{
return a<b?a:b;
}
struct node
{
ll l,r;
mutable bool v;
node(ll L, ll R=-1, bool V=0):l(L), r(R), v(V) {}
bool operator<(const node& o) const
{
return l < o.l;
}
};
set<node> s;
ll ans=1;
inline IT split(register ll pos)
{
IT it = s.lower_bound(node(pos));
if (it != s.end() && it->l == pos)
return it;
--it;
ll L = it->l, R = it->r;
bool V = it->v;
s.erase(it);
s.insert(node(L, pos-1, V));
return s.insert(node(pos, R, V)).first;
}
inline void findnext()
{
IT it = split(ans);
for(;;++it)
if(!it->v)
{
ans=it->l;
return;
}
}
inline void assign_val(register ll l,register ll r,register bool val)
{
IT itr = split(r+1),itl = split(l);
s.erase(itl, itr);
s.insert(node(l, r, val));
if(val&&l<=ans&&ans<=r)
findnext();
else if(!val)
ans=Min(ans,l);
}
inline void reverse(register ll l,register ll r)
{
IT itr = split(r+1),itl = split(l);
bool f=true;
if(l<=ans&&ans<=r)
{
for(; itl != itr; ++itl)
{
itl->v^=1;
if(f&&!itl->v)
{
f=false;
ans=itl->l;
}
}
if(f)
findnext();
}
else
for(; itl != itr; ++itl)
{
itl->v^=1;
if(f&&!itl->v)
{
f=false;
ans=Min(ans,itl->l);
}
}
}
int main()
{
int q=read();
s.insert(node(1,1e19,0));
while(q--)
{
int opt=read();
ll l=read(),r=read();
if(opt==1)
assign_val(l,r,1);
else if(opt==2)
assign_val(l,r,0);
else
reverse(l,r);
write(ans),puts("");
}
return 0;
}
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