UVa1471

保留有价值的数字的做法，实际上这道题因为n只有1e5，所以不需要这种优化。

 #include<bits/stdc++.h>

 #define inf 0x3f3f3f3f

 const int maxn=;

 using namespace std;

 int t;

 int n;

 struct node{
         int val;
         int dpl,dpr;
         bool operator < (const node &rhs) const{
                 if(val == rhs.val)
                 return dpl < rhs.dpl;
                 else return val < rhs.val;
         }
 }a[maxn+];

 set<node> s;

 void init(){
         s.clear();
         memset(a, , sizeof(a));
         scanf("%d",&n);
         for(int i = ; i <= n; ++i){
                 scanf("%d", &a[i].val);
         }
         for(int i = n; i >= ; --i){
                 if(a[i].val < a[i+].val){
                         a[i].dpr = a[i+].dpr + ;
                 } else{
                         a[i].dpr = ;
                 }
         }

 }

 int solve(){
       int res = ;
         for(int i = ; i <= n; ++i){
                 if(a[i].val > a[i-].val){
                         a[i].dpl = a[i-].dpl + ;
                 } else {
                         a[i].dpl = ;
                 }
                  set<node>::iterator it1 = s.lower_bound(a[i]);
                         if(it1 != s.begin()){
                                 --it1;
                                 res = max(res, (*it1).dpl + a[i].dpr);
                         } else res = max(res, a[i].dpr);
                 if(i == ){
                 s.insert(a[i]);
                 continue;
                 }
                 set<node>::iterator it = s.lower_bound(a[i]);
                 set<node>::iterator temp = it;
                 if(it != s.begin()){
                       --it;
                       if((*it).dpl >= (a[i]).dpl){
                         continue;
                       }
                 }
                 it = temp;
                         while(it != s.end()){
                                 if((*it).dpl <= a[i].dpl){
                                         it = s.erase(it);
                                 } else {
                                         break;
                                 }
                         }
                         s.insert(a[i]);
         }
         return res;
 }

 int main()
 {
         scanf("%d",&t);
         while(t--){
                 init();
                 int ans = solve();
                 printf("%d\n", ans);
         }
     return ;
 }