interviewstreet pair

#include <iostream>
#include <algorithm>
using namespace std;

int main()
{
    int N, K;
    cin >> N >> K;
    long long *key = new long long[N];

    for (int i = 0; i < N; i++)
    {
        cin >> key[i];
    }
    sort (key, key+N);                     //对数组进行排序
    int k = 0;
    for (int i = 0; i < N; i++)
    {
        int begin = i+1;
        int end = N-1;
        int value = key[i] + K;
        while(begin <= end)                //用二分查找有没有满足条件的
        {
            int mid = (begin+end)/2;
            if (key[mid] < value)
                begin = mid + 1;
            else if (key[mid] > value)
                end = mid - 1;
            else
            {
                k++;
                break;
            }
        }
    }
    cout << k << endl;  
}