HDU 4398 Template Library Management (最优页面调度算法)

中等偏易题。操作系统理论中的最优页面调度算法，贪心。当需要淘汰某个模版时，淘汰掉当前手中在最远的将来才会被用到（或者以后永远不再用到）的那个。
 

代码：

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <cmath>
#include <algorithm>
#include <string>
#include <queue>
#include <stack>
#include <vector>
#include <map>
#include <set>
#include <functional>
#include <time.h>

using namespace std;

typedef pair<int, int> PII;

const int INF = 1<<30;
const int MAXN = (int) 1e5+11;

priority_queue<PII> q;
int Ti[MAXN], next[MAXN];
int Find[MAXN], len; //离散化用
int vis[MAXN]; //计算下一次出现用
bool inq[MAXN]; //判断是否拥有
int N, M;

void input() {
    for (int i = 0; i < N; i++)
        scanf("%d", &Ti[i]);
}

void solve() {
    //离散化
    for (int i = 0; i < N; i++)
        Find[i] = Ti[i];
    sort(Find, Find+N);
    len = unique(Find, Find+N) - Find;
    for (int i = 0; i < N; i++)
        Ti[i] = lower_bound(Find, Find+len, Ti[i]) - Find;

    //计算next[]
    for (int i = 0; i <= len; i++) vis[i] = N+1; //初始化vis[]
    for (int i = N-1; i >= 0; i--) {
        next[i] = vis[Ti[i]];
        vis[Ti[i]] = i;
    }

    int ans = 0, have = 0;
    while (!q.empty()) q.pop(); //初始化队列
    memset(inq, false, sizeof(inq));
    for (int i = 0, j = 0; i < M; i++) { //一开始就有的模板
        int t = Find[j]==(i+1) ? j++ : len;
        q.push(make_pair(vis[t], t));
        inq[t] = true;
        have++;
    }

    for (int i = 0; i < N; i++) {
        if (!inq[Ti[i]]) { //如果现在没有有这个模板，那么就要去借
            have++;
            ans++;
        }
        //把那个模板拿过来
        inq[Ti[i]] = true;
        q.push(make_pair(next[i], Ti[i]));

        if (have>M) { //需要丢弃模板
            PII x = q.top(); q.pop();
            inq[x.second] = false;
            have--;
        }
    }

    printf("%d
", ans);
}

int main() {
    #ifdef Phantom01
        freopen("I.txt", "r", stdin);
    #endif //Phantom01

    while (scanf("%d%d", &N, &M)!=EOF) {
        input();
        solve();
    }

    return 0;
}