1421 - Wavio Sequence

题目大意：求一个序列中 先严格递增后严格递减的子序列的数目（要求这个子序列对称）。

题目思路：正一遍DP,反一遍DP，因为n<=1e5，dp要把时间压缩到nlogn

#include<stdio.h>
#include<string.h>
#include<iostream>
#include<algorithm>
#define MAXSIZE 100005

using namespace std;

int dp[MAXSIZE],a[MAXSIZE];

int n;

int Solve()
{
    dp[] = ;
    int G1[MAXSIZE],G2[MAXSIZE],len=,pos;
    G1[] = a[];
    for(int i=;i<=n;i++)
    {
        if(a[i] > G1[len])
            pos = ++len;
        else
        {
            pos = lower_bound(G1+,G1++len,a[i]) - (G1+) + ;
        }
        G1[pos] = a[i];
        dp[i] = len;
    }

    G2[] = a[n];
    len = ;
    int ans = ;
    for(int i=n-;i>=;i--)
    {
        if(a[i] > G2[len])
            pos = ++len;
        else
            pos = lower_bound(G2+,G2++len,a[i]) - (G2+) + ;
        G2[pos] = a[i];
        int temp = min(len,dp[i]);
        ans = max(ans,temp);
    }
    return *ans - ;
}

int main()
{
    int T,cns=;
    scanf("%d",&T);
    while(T--)
    {
        scanf("%d",&n);
        for(int i=;i<=n;i++)
            scanf("%d",&a[i]);
        int ans =Solve();
        printf("Case %d: %d\n",cns++,ans);
    }
    return ;
}