hdu 6197array array array（最长不下降子序列nlogn）

Problem Description
One day, Kaitou Kiddo had stolen a priceless diamond ring. But detective Conan blocked Kiddo’s path to escape from the museum. But Kiddo didn’t want to give it back. So, Kiddo asked Conan a question. If Conan could give a right answer, Kiddo would return the ring to the museum.
Kiddo: “I have an array A and a number k, if you can choose exactly k elements from A and erase them, then the remaining array is in non-increasing order or non-decreasing order, we say A is a magic array. Now I want you to tell me whether A is a magic array. ” Conan: “emmmmm…” Now, Conan seems to be in trouble, can you help him?

Input
The first line contains an integer T indicating the total number of test cases. Each test case starts with two integers n and k in one line, then one line with n integers: A1,A2…An.
1≤T≤20
1≤n≤10^5
0≤k≤n
1≤Ai≤10^5

Output
For each test case, please output “A is a magic array.” if it is a magic array. Otherwise, output “A is not a magic array.” (without quotes).

Sample Input
3
4 1
1 4 3 7
5 2
4 1 3 1 2
6 1
1 4 3 5 4 6

Sample Output
A is a magic array.
A is a magic array.
A is not a magic array.

大致题意：给你n个数，问让你从中删掉k个数后（k<=n），是否能使剩下的序列为非递减或者非递增序列

思路：签到题，就是让你求最长不下降子序列长度len，然后判断下n-len是否小于k（将序列反着存下来然后再求即最长不上升子序列，取两者len中的较大值），然后直接套nlogn的模板即可。

代码如下

#include
#include
#include
#include
#include
#include
#include
#include
#define LL long long  
const int maxn=1e5+5;
using namespace std;
int a[maxn],b[maxn],c[maxn];
int n;
int LIS(int *d){
    memset(c,0,sizeof(c));
    c[1]=d[1];
    int l,r,mid,len=1;
    for(int i=2;i<=n;i++){
        l=1;
        r=len;
        while(l<=r){    
        mid=(l+r)/2;
        if(c[mid]<=d[i]) l=mid+1;
        else  r=mid-1;
        }
        c[l]=d[i];
        if(l>len) len++;

    }
    return len;
}
int main()
{
    int T;
    scanf("%d",&T);
    int k;
    while(T--)
    {
        scanf("%d%d",&n,&k);
        for(int i=1;i<=n;i++)
        {
            scanf("%d",&a[i]);
            b[n-i+1]=a[i];
        }
        int maxn=max(LIS(a),LIS(b));

        if(n-maxn>k)
        printf("A is not a magic array.\n");
        else 
        printf("A is a magic array.\n");
    }   
    return 0;
}