【BZOJ】【P1826&P1528】【JSOI2010】【缓存交换】【题解】【堆+贪心】

传送门:http://www.lydsy.com/JudgeOnline/problem.php?id=1826http://www.lydsy.com/JudgeOnline/problem.php?id=1528

结论:每次删掉距离下次使用最远的元素最优

证明待填坑

Code:

#include<bits/stdc++.h>
using namespace std;
const int maxn=1e5+5;
typedef pair<int,int> pii;
priority_queue<pii,vector<pii> >q;
int n,m,tot,next[maxn],a[maxn];
map<int,int>M;
short in[maxn];
int main(){
scanf("%d%d",&n,&m);
for(int i=1;i<=n;i++){
scanf("%d",&a[i]);
if(!M[a[i]])M[a[i]]=++tot;
a[i]=M[a[i]];
}M.clear();
for(int i=n;i;i--){
if(!M[a[i]])M[a[i]]=i,next[i]=1e9;
else next[i]=M[a[i]],M[a[i]]=i;
}int ans=0,size=0;
for(int i=1;i<=n;i++){
if(in[a[i]]){
q.push(pii(next[i],a[i]));
continue;
}ans++;in[a[i]]=1;
if(size==m){in[q.top().second]=0;q.pop();size--;}
q.push(pii(next[i],a[i]));size++;
}cout<<ans<<endl;
return 0;
}