2025“钉耙编程”中国大学生算法设计暑期联赛（6）——传送排序 · znzryb
## 思路讲解
[P2880 [USACO07JAN] Balanced Lineup G](/2025/01/20/20250120-59915ab4)
用树状数组RMQ。
## AC代码
[https://acm.hdu.edu.cn/contest/view-code?cid=1177&rid=12260](https://acm.hdu.edu.cn/contest/view-code?cid=1177&rid=12260)
::: 源代码
```cpp
// by Gospel_rock
#include <algorithm>
#include <bits/stdc++.h>
#define all(vec) vec.begin(),vec.end()
#define pb push_back
#define EB emplace_back
#define EM emplace
#define FI first
#define SE second
#define pct __builtin_popcountll
#define ctz __builtin_ctzll
#define SZ(a) ((long long) a.size())
#define FOR(i, a, b) for (long long i = (a); i <= (b); ++i)
#define ROF(i, a, b) for (long long i = (a); i >= (b); --i)
#define debug(var) cerr << #var <<":"<<var<<"\n";
#define cend cerr<<"\n-----------\n"
#define lson(var) (var<<1)
#define rson(var) ((var<<1)+1)
#define fsp(x) fixed<<setprecision(x)
using namespace std;
using ll = long long;using ull = unsigned long long;
using DB=double;using LD=long double;
// using i128 = __int128;
using pdd = pair<DB,DB>;using plb = pair<ll,bool>;
using pll = pair<ll,ll>;using vll=vector<ll>;using vb=vector<bool>;
using tll = tuple<ll,ll,ll>;
using vpll = vector<pll>;using vtll = vector<tll>;
using vdb = vector<DB>;using vc=vector<char>;
using arr3 = array<ll,3> ;using arr2 = array<ll,2>;
static constexpr ll MAXN=(ll)1e6+10,INF=(ll)1e17+9; // 1e18+9也是素数
static constexpr ll mod=(ll)1e9+7; // 998244353;
static constexpr double eps=1e-8;const double pi=acos(-1.0);
ll N,M,Q,X,K,T,lT;
inline void __();
signed main()
{
ios::sync_with_stdio(false);
cin.tie(0);cout.tie(0);
cin>>lT;
while(lT--)
__();
return 0;
}
/*
*/
// by Gospel_rock znzryb
// 参考了（抄了）OIwiki
// https://www.luogu.com.cn/record/228807838 ST表模版题（max）
// https://www.luogu.com.cn/record/228809172 打乱了插入顺序，和上面是同一道
struct RMQ{
using ll = long long;
ll n;vector<ll> tr;bool ismax;vector<ll> origin;
inline ll lowbit(const ll &x){
return x&-x;
}
private:
ll get(const ll &a,const ll &b){
if(ismax){
return max(a,b);
}else{
return min(a,b);
}
}
ll set(){
if(ismax) return -INF;
else return INF;
}
public:
RMQ(ll n,bool ismax=true){ // origin[i] 初始化就是 0
this->n=n;this->ismax=ismax;
if(ismax) tr.resize(n+5,-INF),origin.resize(n+5);
else tr.resize(n+5,INF),origin.resize(n+5);
}
ll query(ll l,ll r){
ll res=set();
while (r>=l) {
res=get(origin[r],res);
r--;
for(;r-lowbit(r)>=l;r-=lowbit(r)){
res=get(res, tr[r]);
}
}
return res;
}
void upd(ll p,ll x){
origin[p]=x;
for(int i=p;i<=n;i+=lowbit(i)){ // 枚举受影响的区间
tr[i]=origin[i];
for(int j=1;j<lowbit(i);j<<=1){
tr[i]=get(tr[i],tr[i-j]);
}
}
}
};
inline void __(){
cin>>N;
vll A(N),pos(N+5);
FOR(i,1,N){
cin>>A[i-1];
pos[A[i-1]]=i-1;
}
if(N==1){
cout<<0<<"\n";
return;
}
RMQ tr(N);
vb vis(N+5);
FOR(i,1,N){
ll val=A[i-1];
vis[val]=true;
ll res=tr.query(1, val-1);
if(res==-INF) res=0;
ll lans=tr.origin[val-1]+vis[val-1]+(val==1 || val==N);
// 第一次WA是WA在这里
lans=max(lans,res+(val==1 || val==N));
tr.upd(val, lans);
}
ll ans=tr.query(1, N);
#ifdef LOCAL
FOR(i,1,N){
cerr<<tr.origin[i]<<" ";
}
cend;
#endif
ans=N+1-ans;
cout<<ans<<"\n";
}
/*
WA
https://acm.hdu.edu.cn/contest/view-code?cid=1177&rid=12203
AC
https://acm.hdu.edu.cn/contest/view-code?cid=1177&rid=12260
*/
```
:::
## 心路历程（WA，TLE，MLE……）
1和n的超距作用。
[https://acm.hdu.edu.cn/contest/view-code?cid=1177&rid=12203](https://acm.hdu.edu.cn/contest/view-code?cid=1177&rid=12203)
```cpp
FOR(i,1,N){
ll val=A[i-1];
vis[val]=true;
ll res=tr.query(1, val-1);
if(res==-INF) res=0;
ll lans=tr.origin[val-1]+vis[val-1]+(val==1 || val==N);
// 第一次WA是WA在这里
lans=max(lans,res+(val==1 || val==N));
tr.upd(val, lans);
}
```