问题：As an experienced ACMer, you must have known the importance of "code template library". With the help of pre-printed code library, you can implement the complicated algorithms correctly and efficiently. However, the size of the library is strictly limited during the contest. For example, you can only take at most 25 pages of printed codes in World Finals. So you must choose carefully which code template should be included.
Now your team is participating a programming contest whose rules are slightly different from ICPC. This contest consists of N problems, and you must solved them in order: Before you solve the (i+1)th problem, you must solve the ith problem at first. And solving the ith problem requires a specified code template Ti.
You are allowed to hold M code templates only. At the beginning of the contest, your are holding templates numbered 1, 2, ..., M. During the contest, if the problem you are trying to solve requires code template Ti, and Ti is happened at your hand (i.e, one of the M code templates you are holding is Ti), you can solve it immediately. On the other hand, if you are not holding Ti, you must call your friends who are outside the arena for help (yes, it is permitted, not cheating). They can give you the code template you need. Because you are only allowed to hold M code templates, after solving current problem, you must choose to drop the code you get from your friends just now, or to keep it and drop one of the M templates at your hand previously.
Given the problem sequence in the contest and the limitation M, you want finish all the problems with minimum number of calling your friends.
Input
The first line of each test case contains two numbers N (1 <= N <= 100000) and M (1 <= M <= 100000). The second line contains N numbers T1, T2, ..., TN (1 <= Ti <= 109), indicating the code templates required by each problem.
Output
Output one line for each test case, indicating the minimum number of calling friends for help.
Sample Input
4 3
1 2 3 4
11 3
4 1 2 1 5 3 4 4 1 2 3
Sample Output
1
4
回答：贪心，最优调度算法。维护一个M个元素的集合，根据当前位置的元素的下一个位置选择，删除下一个位置最远的元素。
#include<stdio.h>
#include<iostream>
#include<string.h>
#include<algorithm>
#include<queue>
#include<map>
#include<set>
using namespace std;
const int MAXN=100010;
int Ti[MAXN];
int next[MAXN];
map<int,int>mp;
struct Node
{
int next_id;
int ti;
};
struct classcomp
{
bool operator()(const Node &a,const Node &b)const
{
return a.next_id<b.next_id;//从小到大排序
}
};
multiset<Node,classcomp>T_info;
multiset<Node>::iterator it_n;
set<int>Te;
set<int>::iterator it;
int main()
{
// freopen("in.txt","r",stdin);
// freopen("out.txt","w",stdout);
int n,m;
while(scanf("%d%d",&n,&m)==2)
{
for(int i=1;i<=n;i++)
scanf("%d",&Ti[i]);
mp.clear();//清空map
for(int i=n;i>=1;i--)//从后往前扫描
{
if(mp[Ti[i]])//出现过
next[i]=mp[Ti[i]];
else next[i]=n+1;
mp[Ti[i]]=i;
}
Te.clear();
T_info.clear();
for(int i=1;i<=m;i++)//先把前面带的m个模板入set
{
if(!mp[i])mp[i]=n+1;
Node temp;
temp.next_id=mp[i];
temp.ti=i;
T_info.insert(temp);
Te.insert(i);
}
int ans=0;
for(int i=1;i<=n;i++)
{
it=Te.find(Ti[i]);
if(it!=Te.end())
{
Node temp;
temp.next_id=i;
temp.ti=Ti[i];
T_info.erase(temp);
temp.next_id=next[i];//更新
T_info.insert(temp);
}
else
{
ans++;
it_n=T_info.end();
it_n--;
if(next[i]<(*it_n).next_id)
{
Te.erase((*it_n).ti);
T_info.erase(it_n);
Te.insert(Ti[i]);
Node temp;
temp.next_id=next[i];
temp.ti=Ti[i];
T_info.insert(temp);
}
}
}
printf("%d
",ans);
}
return 0;
}