PAT甲级-1085 Perfect Sequence (25 分)

题目：1085 Perfect Sequence (25 分)

分析：查找，使用二分法

#include <iostream>
#include<cstring>
#include<vector>
#include<stdio.h>
#include<queue>
#include<math.h>
#include<stack>
#include<algorithm>
#include<map>
#include<set>
#include<iostream>
using namespace std;
#define MAX 999999999
typedef long long ll;
ll n,m,k;
int main()
{
    cin>>n>>m;
    ll a[n + 1];
    for(int i = 1; i <= n ;i++)
        cin>>a[i];
    sort(a + 1 ,a + n + 1);
    ll l = 0;
    for(ll i = 1; i <= n ;i ++)
    {
        ll left = i + 1;
        ll right = n;
        ll mid ;
        ll x = a[i] * m;
        while(left < right)
        {
            mid = (left +right ) / 2;
            if(a[mid] < x) left = mid + 1;
            else right = mid;
        }
        if(right - i + 1 > l && a[right] <= x) l = right - i + 1;
    }
    cout<<l;
    return 0;
}