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=200000;

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+10];

set<node> s;

void init(){
        s.clear();
        memset(a, 0, sizeof(a));
        scanf("%d",&n);
        for(int i = 1; i <= n; ++i){
                scanf("%d", &a[i].val);
        }
        for(int i = n; i >= 1; --i){
                if(a[i].val < a[i+1].val){
                        a[i].dpr = a[i+1].dpr + 1;
                } else{
                        a[i].dpr = 1;
                }
        }

}

int solve(){
      int res = 0;
        for(int i = 1; i <= n; ++i){
                if(a[i].val > a[i-1].val){
                        a[i].dpl = a[i-1].dpl + 1;
                } else {
                        a[i].dpl = 1;
                }
                 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 == 1){
                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 0;
}