2017 ACM/ICPC Asia Regional Shenyang Online array array array

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?

题意：去掉一些数字。可以保证是不严格递增或者递减

解法：

求一波最长就行了

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<iostream>
#include<bitset>
#include<vector>
#include<cmath>
#include<bitset>
#include<map>
using namespace std;
const int N=123456;
int b[N];
int LIS1(int a[], int n) {
  int len = 1; b[0] = a[0];
  for (int i = 1; i < n; i++) {
    b[a[i] >= b[len - 1] ? len++ : upper_bound(b, b + len, a[i]) - b] = a[i]; 
  }
  return len;
}
int LIS2(int a[], int n) {
  int len = 1; b[0] = a[0];
  for (int i = 1; i < n; i++) {
    b[a[i] <= b[len - 1] ? len++ : lower_bound(b, b + len, a[i]) - b] = a[i]; 
  }
  return len;
}
int a[N];
int c[N];
int main()
{
    int t;
    scanf("%d",&t);
    while(t--){
       int n,k;
       scanf("%d%d",&n,&k);
       for(int i=0;i<n;i++){
        scanf("%d",&b[i]);
        }
        int x=LIS1(b,n);
        int y=LIS2(b,n);
        if(x+k>=n||y+k>=n){
            cout<<"A is a magic array."<<endl;
        }else{
            cout<<"A is not a magic array."<<endl;
        }
    }
    return 0;
}