Alarm Clock (尺取法)
Every evening Vitalya sets n alarm clocks to wake up tomorrow. Every alarm clock rings during exactly one minute and is characterized by one integer ai — number of minute after midnight in which it rings. Every alarm clock begins ringing at the beginning of the minute and rings during whole minute.
Vitalya will definitely wake up if during some m
Vitalya is so tired that he wants to sleep all day long and not to wake up. Find out minimal number of alarm clocks Vitalya should turn off to sleep all next day. Now all alarm clocks are turned on.
Input
First line contains three integers n, m and k (1 ≤ k ≤ n ≤ 2·105, 1 ≤ m ≤ 106) — number of alarm clocks, and conditions of Vitalya's waking up.
Second line contains sequence of distinct integers a1, a2, ..., an (1 ≤ ai ≤ 106) in which ai equals minute on which i-th alarm clock will ring. Numbers are given in arbitrary order. Vitalya lives in a Berland in which day lasts for 106 minutes.
Output
Output minimal number of alarm clocks that Vitalya should turn off to sleep all next day long.
Examples
Input
3 3 2 3 5 1
Output
1
Input
5 10 3 12 8 18 25 1
Output
0
Input
7 7 2 7 3 4 1 6 5 2
Output
6
Input
2 2 2 1 3
Output
0
Note
In first example Vitalya should turn off first alarm clock which rings at minute 3.
In second example Vitalya shouldn't turn off any alarm clock because there are no interval of 10 consequence minutes in which 3 alarm clocks will ring.
In third example Vitalya should turn off any 6 alarm clocks.
題意:給n個時間點ai-an,表示鬧鐘是在這個時間點響的,m表示時間段,k表示K個鬧鐘,在m這個時間段裡有k個鬧鐘響,就能把他吵醒,問,最少關了多少個鬧鐘,可以讓他不被鬧鐘吵醒,
具體看程式碼就能理解,用到的知識點是尺取法
#include <iostream>
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<algorithm>
using namespace std;
const int N=1000001;
int a[N];
int b[N];
int main()
{
int n,m,k;
scanf("%d%d%d",&n,&m,&k);
for(int i=0; i<n; i++)
scanf("%d",&a[i]);
sort(a,a+n);
int l,r;
l=r=1;
int ans=0;
for(int i=0; i<n; i++)
{
b[r]=a[i];
if(r-l+1==k)
{
if(b[r]-b[l]<m)
{
ans++;
r--;
}
else l++;
}
r++;
}
printf("%d\n",ans);
return 0;
}