PAT_A1085#Perfect Sequence

Source:

PAT A1085 Perfect Sequence (25 分)

Description:

Given a sequence of positive integers and another positive integer p. The sequence is said to be a perfect sequence if M≤m×p where M and m are the maximum and minimum numbers in the sequence, respectively.

Now given a sequence and a parameter p, you are supposed to find from the sequence as many numbers as possible to form a perfect subsequence.

Input Specification:

Each input file contains one test case. For each case, the first line contains two positive integers N and p, where N (≤) is the number of integers in the sequence, and p (≤) is the parameter. In the second line there are N positive integers, each is no greater than 1.

Output Specification:

For each test case, print in one line the maximum number of integers that can be chosen to form a perfect subsequence.

Sample Input:

10 8
2 3 20 4 5 1 6 7 8 9

Sample Output:

8

Keys:

• 双指针

Code:

#include<cstdio>
#include<algorithm>
using namespace std;
const int M=1e5+10;
typedef long long LL;

int main()
{
#ifdef ONLINE_JUDGE
#else
    freopen("Test.txt", "r", stdin);
#endif // ONLINE_JUDGE

    LL n,p,s[M];
    scanf("%lld%lld", &n,&p);
    for(LL i=0; i<n; i++)
        scanf("%lld", &s[i]);
    sort(s,s+n);
    LL i=0,j=1,step=1;
    while(j < n)
    {
        while(j<n && s[j]<=s[i]*p)
            j++;
        if(j-i > step)
            step = j-i;
        i++;
        j=i+step;
    }
    printf("%lld", step);

    return 0;
}