bzoj1826[jsoi2010]：缓存交换(贪心+优先队列)

传送门：http://www.lydsy.com:808/JudgeOnline/problem.php?id=1826

写一写画一画可以发现，当不得不弹出一个主存单元时，弹出下一次出现最晚的一定是最优的。

于是优先队列搞之。。。

#include <iostream>
#include <cstdio>
#include <cstring>
#include <queue>
#include <map>
#include <algorithm>
using namespace std;
const int maxn = 100010;
int a[maxn], nxt[maxn];
map <int, int> s, vis;
int n, m, ans;
struct node {
    int x, val;
    node() {}
    node(int k, int b) {
        x = k; val = b;
    }
    bool operator < (node t) const {
        return val < t.val;
    }
};
priority_queue <node> q;
int main() {
    scanf("%d%d", &n, &m);
    for(int i = 1; i <= n; i ++) {
        scanf("%d", &a[i]);
    }
    for(int i = n; i ; i --) {
        if(s.count(a[i])) nxt[i] = s[a[i]];
        else nxt[i] = n + 1;
        s[a[i]] = i;
    }
    int tot = 0;
    for(int i = 1; i <= n; i ++) {
        if(vis[a[i]] == 1) {
            q.push(node(a[i], nxt[i]));
            continue;
        }
        if(tot == m) {
            tot --;
            while(!q.empty()) {
                node t = q.top();
                q.pop();
                if(vis[t.x] == 0) continue;
                vis[t.x] = 0;
                break;
            }
        }
        ans ++;
        vis[a[i]] = 1;
        q.push(node(a[i], nxt[i]));
        tot ++;
    }
    printf("%d\n", ans);
    return 0;
}